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{{Short description|Symbol placed before units of digital information to indicate multiplication by a power of two}}
The ] defines a system of prefixes (nano-, micro-, milli-, kilo-, mega-, giga- etc.) and symbols (n, µ, m, k, M, G, etc.) that denote powers of ten. When discussing things that naturally come in powers of two, due to ] addressing (such as ] sizes) it is convenient to abbreviate as well, but the SI prefixes do not fit this purpose perfectly, and various conventions have been used to designate power-of-two prefixes.
{{About|powers-of-two prefixes for measurement units like bit and byte|notations for the radix of a numeral|Integer literal#Affixes}}
{{Use dmy dates|date=May 2019|cs1-dates=y}}
{{Redirect|Gibi|other uses|Gibi (disambiguation)}}


{{Bit and byte prefixes}}
== History ==
For instance, 1,024 (2<sup>10</sup>) bytes is accurately designated as 1.0 kilobytes to two significant digits. In the absence of other information, it is never clear what an author means by k (or K) for any power of 2 lower than 2<sup>15</sup>. "32k" equals 32,000 according to the SI usage or 2<sup>15</sup>=32,768 in the power-of-two usage; the latter rounds to 33k in the SI.


A '''binary prefix''' is a ] that indicates a ] of a ] by an integer ]. The most commonly used binary prefixes are '''kibi''' (symbol Ki, meaning {{nowrap|1=2<sup>10</sup> = 1024}}), '''mebi''' ({{nowrap|1=Mi, 2<sup>20</sup> = {{val|1048576}}}}), and '''gibi''' ({{nowrap|1=Gi, 2<sup>30</sup> = {{val|1073741824}}}}). They are most often used in ] as multipliers of ] and ], when expressing the capacity of ]s or the size of computer ].
This led to much confusion about the meaning of the ]es combined with "byte" (], ], ], etc.).


The binary prefixes "kibi", "mebi", etc. were defined in 1999 by the ] (IEC), in the ] ] (Amendment 2). They were meant to replace the ] ] prefixes, such as "kilo" ({{nowrap|1=k, 10<sup>3</sup> = 1000}}), "mega" ({{nowrap|1=M, 10<sup>6</sup> = {{val|1000000}}}}) and "giga" ({{nowrap|1=G, 10<sup>9</sup> = {{val|1000000000}}}}),<ref name="BIPM8" /> that were commonly used in the computer industry to indicate the nearest powers of two. For example, a memory module whose capacity was specified by the manufacturer as "2&nbsp;megabytes" or "2&nbsp;MB" would hold {{nowrap|2 × 2<sup>20</sup>}} = {{nowrap|{{val|2097152}} bytes}}, instead of {{nowrap|2 × 10<sup>6</sup>}} = {{val|2000000}}.
The practice of using binary-based prefixes for computer memory arose as early as 1964.<ref>"," ©1964 gives memory capacity ranges of the various models in "Capacity 8 bit bytes 1 KB = 1024"</ref>


On the other hand, a hard disk whose capacity is specified by the manufacturer as "10 gigabytes" or "10&nbsp;GB", holds {{nowrap|10 × 10<sup>9</sup>}} = {{val|10000000000}} bytes, or a little more than that, but less than {{nowrap|10 × 2<sup>30</sup>}} = {{val|10737418240}} and a file whose size is listed as "2.3&nbsp;GB" may have a size closer to {{nowrap|2.3 × 2<sup>30</sup>}} ≈ {{val|2470000000}} or to {{nowrap|2.3 × 10<sup>9</sup>}} = {{val|2300000000}}, depending on the ] or ] providing that measurement. This kind of ambiguity is often confusing to computer system users and has resulted in ]s.<ref name="suitxxxx" /><ref name="sand2021" /> The IEC 60027-2 binary prefixes have been incorporated in the ] standard and are supported by other standards bodies, including the ], which defines the SI system,<ref name="BIPM8" />{{rp|p.121}} the ] ],<ref name="NIST1" /><ref name="NIST2" /> and the ].
As storage size increased, binary meaning was also extended to higher SI prefixes, such as mega, M, and giga, G, where differences become greater.


Prior to the 1999 IEC standard, some industry organizations, such as the ] (JEDEC), attempted to redefine{{citation needed|reason=We need sources that give specifics: it seems probable that no more than a mention of common use was made.|date=December 2024}} the terms ''kilobyte'', ''megabyte'', and ''gigabyte'', and the corresponding symbols ''KB'', ''MB'', and ''GB'' in the binary sense, for use in storage capacity measurements. However, other computer industry sectors (such as ]) continued using those same terms and symbols with the decimal meaning. Since then, the major standards organizations have expressly disapproved the use of SI prefixes to denote binary multiples, and recommended or mandated the use of the IEC prefixes for that purpose, but the use of SI prefixes in this sense has persisted in some fields.
In January ], the ] introduced the prefixes ''kibi-'', ''mebi-'', ''gibi-'', etc., and the symbols Ki, Mi, Gi, etc. to specify binary multiples of a quantity and eliminate this ambiguity.<ref>Amendment 2 to IEC International Standard ]-2: Letter symbols to be used in electrical technology — Part 2: Telecommunications and electronics </ref> The names for the new standard are derived from the first two letters of the original SI prefixes followed by ''bi'', short for "binary". The new standard also clarifies that, from the point of view of the IEC, the SI prefixes will henceforth only have their base-10 meaning and never have a base-2 meaning.


== Definitions ==
The second edition of the standard<ref>IEC 60027-2 (2000-11) Ed. 2.0</ref> defined them only up to ''exbi''-<ref>{{cite journal|title=Prefixes for binary multiples|author=A.J.Thor|journal=Metrologica|date=2000|volume=37|issue=81|url=http://ej.iop.org/links/rDo33k,Nb/lrUHtuYE3BGiff6cav5vpA/me0112.pdf|format=PDF}}</ref>, but in ], the third edition added prefixes ''zebi''- and ''yobi''-, thus matching all standard SI prefixes with their binary counterparts.<ref>{{cite press release|date=]|title=HERE COME ZEBI AND YOBI|publisher=International Electrotechnical Commission|url=http://www.iec.ch/news_centre/release/nr2005/nr2005.htm}}</ref>
{{anchor|kibi|mebi|gibi|tebi|pebi|exbi|zebi|yobi|robi|quebi|IEC standard prefixes}}


{| style="margin:auto;" class="wikitable"
On ], ] the IEEE standard ]-2002 (Prefixes for Binary Multiples) has been elevated to a full-use standard by the IEEE Standards Association after a two-year trial period.<ref>{{cite web |url=http://standards.ieee.org/board/rev/305agenda.html |title=IEEE-SA STANDARDS BOARD STANDARDS REVIEW COMMITTEE (RevCom) MEETING AGENDA |accessdate=2007-02-25 |date=] |quote='''1541-2002''' (SCC14) IEEE Trial-Use Standard for Prefixes for Binary Multiples '''' <u>Recommendation</u>: Elevate status of standard from trial-use to full-use. Editorial staff will be notified to implement the necessary changes. The standard will be due for a maintenance action in 2007.}}</ref>
|+ Specific units of IEC 60027-2 A.2 and ISO/IEC 80000:13-2008

=== Consumer confusion ===
]es as "160 GB"]]

] uses standard ]es to display a 160×10<sup>9</sup> byte disk as "160.0 GB"]]

In the early days of computers there was little or no consumer confusion because of the sophisticated nature of the consumers and the practice of the computer manufacturers to specify (as opposed to ]) their products with decimal digits of sufficient places, e.g., the 1968 IBM stated System 360 "Model 91s can accommodate up to 6,291,496 bytes of main storage."<ref></ref> The confusion appears to relate to the advent of ]s where there was not enough space to provide sufficient digits to fully state the capacity.{{dubious}}<!-- pure speculation about origins --> In such GUIs, storage capacity was reported in a mixed system of decimal digits and binary prefixes using the SI notation. Apparently, some computer programmers were unaware that disk drive manufacturers used the SI notation when specifying and/or advertising capacity of their ].{{dubious}}<!-- pure speculation about programmers' knowledge --> This mixed presentation appears as early as ]<!-- Mac OS was earlier --> which, for example, would report the space available on a 41,959,424 byte hard disk drive as 40 MB. In ], a 30 gigabyte drive has its capacity reported as both 30,064,771,072 bytes and 28 GB, which makes the precise meaning of the prefixes clearer.<!-- wasn't this in 98, too, though? --> The confusion has sometimes led to ].

== Binary prefixes using SI symbols ==
{|align="center" border="1" cellspacing="0" cellpadding="3" class="wikitable"
|- |-
! colspan="2"|IEC prefix
! Name
! colspan="4"|Representations
! Symbol
! Value
! Base 16
! Base 10
|-
|align="center"| ]
|align="center"| k/K
| 2<sup>10</sup> = 1,024
| = 16<sup>2.5</sup>
| &gt; 10<sup>3</sup>
|-bgcolor="#ffff99"
|align="center"| ]
|align="center"| M
| 2<sup>20</sup> = 1,048,576
| = 16<sup>5</sup>
| &gt; 10<sup>6</sup>
|-
|align="center"| ]
|align="center"| G
| 2<sup>30</sup> = 1,073,741,824
| = 16<sup>7.5</sup>
| &gt; 10<sup>9</sup>
|-bgcolor="#ffff99"
|align="center"| ]
|align="center"| T
| 2<sup>40</sup> = 1,099,511,627,776
| = 16<sup>10</sup>
| &gt; 10<sup>12</sup>
|-
|align="center"| ]
|align="center"| P
| 2<sup>50</sup> = 1,125,899,906,842,624
| = 16<sup>12.5</sup>
| &gt; 10<sup>15</sup>
|-bgcolor="#ffff99"
|align="center"| ]
|align="center"| E
| 2<sup>60</sup> = 1,152,921,504,606,846,976
| = 16<sup>15</sup>
| &gt; 10<sup>18</sup>
|-
|align="center"| ]
|align="center"| Z
| 2<sup>70</sup> = 1,180,591,620,717,411,303,424
| = 16<sup>17.5</sup>
| &gt; 10<sup>21</sup>
|-bgcolor="#ffff99"
|align="center"| ]
|align="center"| Y
| 2<sup>80</sup> = 1,208,925,819,614,629,174,706,176&nbsp;
| = 16<sup>20</sup>
| &gt; 10<sup>24</sup>
|-
|}

The one-letter symbols are identical to SI prefixes, except for "K", which is used interchangeably with "k" (in SI, the upper-case or capital "K" stands for ], and ''only'' the lower-case "k" represents 1,000).

These prefixes are in common use in contexts where accuracy is not important, such as file and memory sizes, but conflict with SI definitions. The names and values of the ] were defined in the 1960 SI standard, with powers-of-1000 values. ], standard dictionaries do not recognize the binary meanings for these prefixes.

] (which maintains ]) expressly prohibits the binary prefix usage, and recommends the use of ] as an alternative (computing units are not included in SI).<ref name="BIPM">
{{cite book |title=The International System of Units (SI) |url=http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf |format=PDF |accessdate=2007-02-25 |edition=8th edition |year=2006 |publisher=STEDI Media |location=Paris |language=French/English |isbn=92-822-2213-6 |pages=p. 127 |chapter=§3.1 SI prefixes |quote= These SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The IEC has adopted prefixes for binary powers in the international standard IEC 60027-2: 2005, third edition, ''Letter symbols to be used in electrical technology — Part 2: Telecommunications and electronics''. The names and symbols for the prefixes corresponding to 2<sup>10</sup>, 2<sup>20</sup>, 2<sup>30</sup>, 2<sup>40</sup>, 2<sup>50</sup>, and 2<sup>60</sup> are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 2<sup>10</sup> B = 1024 B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes.}}
</ref>

Some have suggested that "k" be used for 1,000, and "K" for 1,024, but this cannot be extended to the higher order prefixes and has never been widely recognised.

Although the prefixes denoting fractions of a bit or byte might theoretically find application in areas such as ], ], and data transfer rates, they are not used in practice.

Informally, the prefixes are often used on their own. Thus one might hear about a "256K DRAM" (256 ''binary'' kilobytes), "a 160 MB HDD" (160 ''decimal'' megabytes) or "a 2M Internet connection" (2 ''decimal'' megabits per second). What units are being used, and whether the multipliers are decimal or binary, depends on context and cannot be determined by the units alone.

<gallery>
Image:Apple_Macintosh_Desktop.png|From its beginning in 1984, Apple's ] displayed disk capacity using KB = 1024 bytes; their 400 "KB" floppy disk had a capacity of 409,600 bytes.
Image:Windows XP Disk management for 160 GB disk.png|] state the capacity of a 160×10<sup>9</sup> byte disk drive as "149.05 GB" (binary).
Image:Windows XP Drive Properties for 160 GB disk.png|Windows XP uses to state the capacity of a 160×10<sup>9</sup> byte disk drive as "152625 MB" (binary).
Image:Windows XP C partition properties.png|Windows XP uses state the size of a 73×10<sup>9</sup> byte disk drive partition as "68.1 GB" (binary).
Image:Memory module DDRAM 20-03-2006.jpg|The 536,870,912 byte (512×2<sup>20</sup>) capacity of these RAM modules is stated as "512 MB" (binary).
</gallery>

== IEC standard prefixes ==
{|align="center" border="1" cellspacing="0" cellpadding="3" class="wikitable"
|- |-
! Name ! Name
! Symbol ! Symbol
! Base 2 ! Base 2
!colspan="2"| Base 16 ! Base 1024
! Value
!colspan="2"| Base 10
! Base 10
|- |-
| kibi | kibi
| Ki | Ki
| 2<sup>10</sup> | 2<sup>10</sup>
| 16<sup>2.5</sup> | 1024<sup>1</sup>
|align="right"| 400 | align="right"| {{val|1024}}
| = 1,024 | = {{val|1.024|e=3}}
|- style="background:#eee;"
| &gt; 10<sup>3</sup>
|-bgcolor="#ffff99"
| mebi | mebi
| Mi | Mi
| 2<sup>20</sup> | 2<sup>20</sup>
| 16<sup>5</sup> | 1024<sup>2</sup>
|align="right"| 10&nbsp;0000 | align="right" | {{val|1048576}}
| ≈ {{val|1.049|e=6}}
| = 1,048,576
| &gt; 10<sup>6</sup>
|- |-
| gibi | gibi
| Gi | Gi
| 2<sup>30</sup> | 2<sup>30</sup>
| 16<sup>7.5</sup> | 1024<sup>3</sup>
|align="right"| 4000&nbsp;0000 | align="right" | {{val|1073741824}}
| ≈ {{val|1.074|e=9}}
| = 1,073,741,824
|- style="background:#eee;"
| &gt; 10<sup>9</sup>
|-bgcolor="#ffff99"
| tebi | tebi
| Ti | Ti
| 2<sup>40</sup> | 2<sup>40</sup>
| 16<sup>10</sup> | 1024<sup>4</sup>
|align="right"| 100&nbsp;0000&nbsp;0000 | align="right" | {{val|1099511627776}}
| ≈ {{val|1.100|e=12}}
| = 1,099,511,627,776
| &gt; 10<sup>12</sup>
|- |-
| pebi | pebi
| Pi | Pi
| 2<sup>50</sup> | 2<sup>50</sup>
| 16<sup>12.5</sup> | 1024<sup>5</sup>
|align="right"| 4&nbsp;0000&nbsp;0000&nbsp;0000 | align="right" | {{val|1125899906842624}}
| ≈ {{val|1.126|e=15}}
| = 1,125,899,906,842,624
|- style="background:#eee;"
| &gt; 10<sup>15</sup>
|-bgcolor="#ffff99"
| exbi | exbi
| Ei | Ei
| 2<sup>60</sup> | 2<sup>60</sup>
| 16<sup>15</sup> | 1024<sup>6</sup>
|align="right"| 1000&nbsp;0000&nbsp;0000&nbsp;0000 | align="right" | {{val|1152921504606846976}}
| ≈ {{val|1.153|e=18}}
| = 1,152,921,504,606,846,976
| &gt; 10<sup>18</sup>
|- |-
| zebi | zebi
| Zi | Zi
| 2<sup>70</sup> | 2<sup>70</sup>
| 16<sup>17.5</sup> | 1024<sup>7</sup>
|align="right"| 40&nbsp;0000&nbsp;0000&nbsp;0000&nbsp;0000 | align="right" | {{val|1180591620717411303424}}
| ≈ {{val|1.181|e=21}}
| = 1,180,591,620,717,411,303,424
|- style="background:#eee;"
| &gt; 10<sup>21</sup>
|-bgcolor="#ffff99"
| yobi | yobi
| Yi | Yi
| 2<sup>80</sup> | 2<sup>80</sup>
| 16<sup>20</sup> | 1024<sup>8</sup>
|align="right"| 1&nbsp;0000&nbsp;0000&nbsp;0000&nbsp;0000&nbsp;0000 | align="right" | {{val|1208925819614629174706176}}
| ≈ {{val|1.209|e=24}}
| = 1,208,925,819,614,629,174,706,176
| &gt; 10<sup>24</sup>
|} |}


{{anchor|robi|quebi}}In 2022, the ] (BIPM) adopted the decimal prefixes ] for 1000<sup>9</sup> and ] for 1000<sup>10</sup>.<ref name="BIPM2022" /><ref name="gibn2022" /> In analogy to the existing binary prefixes, a consultation paper of the ]' Consultative Committee for Units (CCU) suggested the prefixes ''robi'' ({{nowrap|Ri, 1024<sup>9</sup>}}) and ''quebi'' ({{nowrap|Qi, 1024<sup>10</sup>}}) for their binary counterparts,<ref name="brown2023" /> but {{as of|2022|lc=yes}}, no corresponding binary prefixes have been adopted.<ref name="brown2022" />
''Example:'' 300&nbsp;GB ≅ 279.5&nbsp;GiB.


=== Approximate ratios between binary and decimal prefixes === == Comparison of binary and decimal prefixes ==
As the order of magnitude increases, the percentage difference between the binary and decimal values of a prefix increases, from 2.4% (with the kilo prefix) to over 20% (with the ''yotta'' prefix). This makes differentiating between the two increasingly important as larger and larger data storage and transmission technologies are developed. The relative difference between the values in the binary and decimal interpretations increases, when using the SI prefixes as the base, from 2.4% for kilo to nearly 27% for the quetta prefix. Although the prefixes ronna and quetta have been defined, as of 2022 no names have been officially assigned to the corresponding binary prefixes.


{| class="wikitable" style="margin: auto;"
{|align="center" border="1" cellspacing="0" cellpadding="3" class="wikitable"
|- style="background:#ccf;"
|-bgcolor="#ccccff"
! colspan="2" | Prefix
! Name
! colspan="2" | Binary ÷ Decimal
! Bin ÷ Dec
! colspan="2" | Decimal ÷ Binary
! Dec ÷ Bin
|- id="binary vs decimal kilo-"
! Example
| kilo || kibi
! Percentage difference
| 1.024 (+2.4%) || class="nowrap" |<div style="display:inline-block;width:102.4px;background:#000"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
|-
| 0.9766 (−2.3%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:97.7px;background:#666;">&nbsp;</div></div>
| ]&nbsp;: ]
|- id="binary vs decimal mega-"
| 1.024
| mega || mebi
| 0.976
| 1.049 (+4.9%) || class="nowrap" | <div style="display:inline-block;width:104.9px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 100&nbsp;kB ≅ 97.6&nbsp;KiB
| 0.9537 (−4.6%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:95.4px;background:#666;">&nbsp;</div></div>
| +2.4% or −2.3%
|- id="binary vs decimal giga-"
|-bgcolor="#ffff99"
| giga || gibi
| ]&nbsp;: ]
| 1.074 (+7.4%) || class="nowrap" | <div style="display:inline-block;width:107.4px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 1.049
| 0.9313 (−6.9%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:93.1px;background:#666;">&nbsp;</div></div>
| 0.954
|- id="binary vs decimal tera-"
| 100&nbsp;MB ≅ 95.4&nbsp;MiB
| +4.9% or −4.6% | tera || tebi
| 1.100 (+10.0%) || class="nowrap" | <div style="display:inline-block;width:110.0px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
|-
| 0.9095 (−9.1%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:90.9px;background:#666;">&nbsp;</div></div>
| ]&nbsp;: ]
|- id="binary vs decimal peta-"
| 1.074
| peta || pebi
| 0.931
| 1.126 (+12.6%) || class="nowrap" | <div style="display:inline-block;width:112.6px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 100&nbsp;GB ≅ 93.1&nbsp;GiB
| 0.8882 (−11.2%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:88.8px;background:#666;">&nbsp;</div></div>
| +7.4% or −6.9%
|- id="binary vs decimal exa-"
|-bgcolor="#ffff99"
| exa || exbi
| ]&nbsp;: ]
| 1.153 (+15.3%) || class="nowrap" | <div style="display:inline-block;width:115.3px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 1.100
| 0.8674 (−13.3%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:86.7px;background:#666;">&nbsp;</div></div>
| 0.909
|- id="binary vs decimal zetta-"
| 100&nbsp;TB ≅ 90.9&nbsp;TiB
| +10% or −9.1% | zetta || zebi
| 1.181 (+18.1%) || class="nowrap" | <div style="display:inline-block;width:118.1px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
|-
| 0.8470 (−15.3%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:84.7px;background:#666;">&nbsp;</div></div>
| ]&nbsp;: ]
|- id="binary vs decimal yotta-"
| 1.126
| yotta || yobi
| 0.888
| 1.209 (+20.9%) || class="nowrap" | <div style="display:inline-block;width:120.9px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 100&nbsp;PB ≅ 88.8&nbsp;PiB
| 0.8272 (−17.3%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:82.7px;background:#666;">&nbsp;</div></div>
| +12.6% or −11.2%
|- id="binary vs decimal yotta-"
|-bgcolor="#ffff99"
| ronna || — <!-- editor note: please do not insert any binary prefix here (e.g. robi) until such a prefix is officially published, e.g. by the IEC -->
| ]&nbsp;: ]
| 1.238 (+23.8%) || class="nowrap" | <div style="display:inline-block;width:123.8px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
| 1.153
| 0.8078 (−19.2%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:80.8px;background:#666;">&nbsp;</div></div>
| 0.867
|- id="binary vs decimal yotta-"
| 100&nbsp;EB ≅ 86.7&nbsp;EiB
| quetta || — <!-- editor note: please do not insert any binary prefix here (e.g. quebi) until such a prefix is officially published, e.g. by the IEC -->
| +15.3% or −13.3%
| 1.268 (+26.8%) || class="nowrap" | <div style="display:inline-block;width:126.8px;background:#000;"><div style="display:inline-block;width:100px;background:#666;">&nbsp;</div></div>
|-
| 0.7889 (−21.1%) || class="nowrap" | <div style="display:inline-block;width:100px;background:#ccc;"><div style="display:inline-block;width:78.9px;background:#666;">&nbsp;</div></div>
| ]&nbsp;: ]
| 1.181
| 0.847
| 100&nbsp;ZB ≅ 84.7&nbsp;ZiB
| +18.1% or −15.3%
|-bgcolor="#ffff99"
| ]&nbsp;: ]
| 1.209
| 0.827
| 100&nbsp;YB ≅ 82.7&nbsp;YiB
| +20.9% or −17.3%
|} |}


=== Adoption === == History ==
{{See also|Timeline of binary prefixes}}
], the ] binary naming convention is not widespread, but its use is growing.


=== Early prefixes ===
It is strongly supported by many standardization bodies and technical organizations, such as ], ], ], and ].<ref name="IEEE">
The original ] adopted by France in 1795 included two binary prefixes named '']-'' (2×) and '']-'' ({{sfrac|1|2}}×).<ref name="frev1795" /> However, these were not retained when the ]es were internationally adopted by the 11th ] in 1960.
{{cite book |title=IEEE Trial-Use Standard for Prefixes for Binary Multiples |url=http://ieeexplore.ieee.org/iel5/8450/26611/01186538.pdf?arnumber=1186538 |format=PDF |accessdate=2007-02-25 |date=] |location=New York |isbn=0-7381-3386-8 |quote=This standard is prepared with two goals in mind: (1) to preserve the SI prefixes as unambiguous decimal multipliers and (2) to provide alternative prefixes for those cases where binary multipliers are needed. The first goal affects the general public, the wide audience of technical and nontechnical persons who use computers without much concern for their construction or inner working. These persons will normally interpret kilo, mega, etc., in their proper decimal sense. The second goal speaks to specialists—the prefixes for binary multiples make it possible for persons who work in the information sciences to communicate with precision.}}
</ref><ref name="BIPM"/><ref name="NIST">
— The NIST Reference on Constants, Units, and Uncertainty
</ref><ref name="SAE">
— Section C.1.12 — SI prefixes
</ref>
The new binary prefixes have also been adopted by the European Committee for Electrotechnical Standardization (]) as the harmonization document HD&nbsp;60027-2:2003-03.<ref name="EUHD"> Information about the harmonization document (obtainable on order)</ref>
This document will be adopted as a ].<ref> Information about the EN standardization process</ref>


=== Storage capacity ===
The prefixes are beginning to be used in technical articles and software where it is important to avoid ambiguity. Examples of software that use IEC standard prefixes (along with standard SI prefixes) include the ],<ref>{{cite web
==== Main memory ====
|url=http://www.annodex.net/cgi-bin/man/man2html?units+7
Early computers used one of two addressing methods to access the system memory; binary (base 2) or decimal (base 10).<ref name="weik1961" /> For example, the ] (1952) used a binary methods and could address 2048 ]s of 36 ]s each, while the ] (1953) used a decimal system, and could address ten thousand 7-bit words.
|title=UNITS
|accessdate=2007-05-20
|date=]
|work=]
|quote=When the Linux kernel boots and says <code>hda: 120064896 sectors (61473 MB) w/2048KiB Cache</code> the MB are megabytes and the KiB are kibibytes.
}}</ref> ],<ref>{{cite web
|url=http://www.gnu.org/software/coreutils/manual/html_chapter/coreutils_2.html#SEC4
|title=2.2 Block size
|accessdate=2007-05-20
|date=]
|work=] manual
|publisher=]
|quote=Integers may be followed by suffixes
that are upward compatible with the for decimal multiples and with the .
}}</ref> ],<ref>{{cite web
|url=http://sourceforge.net/project/shownotes.php?release_id=389304&group_id=115843
|title=gparted-0.2 changelog
|accessdate=2007-05-20
|date=]
|work=]
|quote=changed KB/MB/GB/TB to KiB/MiB/GiB/TiB after reading http://www.iec.ch/zone/si/si_bytes.htm
}}</ref> ],<ref>{{cite web
|url=http://www.annodex.net/cgi-bin/man/man2html?8+ifconfig
|title=IFCONFIG
|accessdate=2007-05-20
|date=]
|work=]
|quote=Since net-tools 1.60-4 ifconfig is printing byte counters and human readable counters with IEC 60027-2 units. So 1 KiB are 2^10 byte.
}}</ref> and ]. Other programs like ] and ] use SI prefixes correctly without using IEC prefixes.


By the mid-1960s, binary addressing had become the standard architecture in most computer designs, and main memory sizes were most commonly powers of two. This is the most natural configuration for memory, as all combinations of states of their ]s map to a valid address, allowing easy aggregation into a larger block of memory with contiguous addresses.
<gallery>
Image:Gnome Partition Editor showing 160 GB disk.png|]'s partition editor uses IEC prefixes to display partition sizes. The total capacity of the 160×10<sup>9</sup> byte disk is displayed as "149.05 ]"
Image:GNOME System Monitor memory size and network rate.png|GNOME's system monitor uses IEC prefixes to show memory size and networking data rate.
Image:Bittornado screenshot showing use of IEC and SI prefixes.png|] uses standard SI prefixes for data rates and IEC prefixes for file sizes
</gallery>


While early documentation specified those memory sizes as exact numbers such as 4096, 8192, or {{val|16384}} units (usually ]s, bytes, or bits), computer professionals also started using the long-established metric system prefixes "kilo", "mega", "giga", etc., defined to be powers of 10,<ref name="BIPM8" /> to mean instead the nearest powers of two; namely, 2<sup>10</sup> = 1024, 2<sup>20</sup> = 1024<sup>2</sup>, 2<sup>30</sup> = 1024<sup>3</sup>, etc.<ref name="blais1930" /><ref name="liny1972" /> The corresponding metric prefix symbols ("k", "M", "G", etc.) were used with the same binary meanings.<ref name="real1959" /><ref name="gruen1960" /> The symbol for 2<sup>10</sup> = 1024 could be written either in lower case ("k")<ref name="horak2008" /><ref name="dodd1997" /><ref name="laver1989" /> or in uppercase ("K"). The latter was often used intentionally to indicate the binary rather than decimal meaning.<ref name="amda1964" /> This convention, which could not be extended to higher powers, was widely used in the documentation of the ] (1964)<ref name="amda1964" /> and of the ] (1972),<ref name="IBM1972" /> of the ],<ref name="CDC7600" /> of the DEC ]/70 (1975)<ref name="bell1975" /> and of the DEC ] (1977).{{citation needed|date=August 2023}}
== Usage notes ==
The phrase "decimal unit" will be used to denote "SI designation understood in its standard, decimal, power-of-1000 sense" and "binary unit" will mean "SI designation understood in its binary, power-of-1024 sense." '''B''' will be used as the symbol for byte as per computer-industry standard (] and ]; '''B''' is also the symbol for ], a common non-SI unit used for ratio measurement).


In other documents, however, the metric prefixes and their symbols were used to denote powers of 10, but usually with the understanding that the values given were approximate, often truncated down. Thus, for example, a 1967 document by ] (CDC) abbreviated "2<sup>16</sup> = {{nowrap|64 × 1024}} = {{val|65536}} words" as "65K words" (rather than "64K" or "66K"),<ref name="CDC1967" /> while the documentation of the ] real-time computer (1974) denoted {{nowrap|3 × 2<sup>16</sup>}} = {{nowrap|192 × 1024}} = {{val|196608}} as "196K" and 2<sup>20</sup> = {{val|1048576}} as "1M".<ref name="frank1974" />
Certain units are always understood as decimal even in computing contexts. For example, ] (Hz), which is used to measure ''']s''' of electronic components, and bit/s, used to measure ''']'''. So a 1 GHz processor performs 1,000,000,000 clock ticks per second, a 128 kbit/s<!--- Truly kbit for kilobit, no Kbit please ---> ] stream consumes 128,000 bits (16 kB, 15.625 KiB) per second, and a 1&nbsp;Mbit/s Internet connection can transfer 1,000,000 bits (125 kB, approx 122 KiB) per second, assuming an 8-bit byte, and no overhead.<ref></ref>


These three possible meanings of "k" and "K" ("1024", "1000", or "approximately 1000") were used loosely around the same time, sometimes by the same company. The ] business computer (1973) could have "64K", "96K", or "128K" bytes of memory.<ref name="HP1973" /> The use of SI prefixes, and the use of "K" instead of "k" remained popular in computer-related publications well into the 21st century, although the ambiguity persisted. The correct meaning was often clear from the context; for instance, in a binary-addressed computer, the true memory size had to be either a power of 2, or a small integer multiple thereof. Thus a "512 megabyte" RAM module was generally understood to have {{nowrap|512 × 1024<sup>2</sup>}} = {{val|536870912}} bytes, rather than {{val|512000000}}.
=== Pronunciation ===
It is suggested that in English, the first syllable of the name of the binary-multiple prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix, and that the second syllable should be pronounced as "bee." <ref name="NIST"/>


=== Computer memory === ==== Hard disks ====
In specifying disk drive capacities, manufacturers have always used conventional decimal SI prefixes representing powers of 10. Storage in a rotating ] is organized in platters and tracks whose sizes and counts are determined by mechanical engineering constraints so that the capacity of a disk drive has hardly ever been a simple multiple of a power of 2. For example, the first commercially sold disk drive, the ] (1956), had 50 physical disk platters containing a total of {{val|50000}} sectors of 100 characters each, for a total quoted capacity of 5 million characters.<ref name="IBM1956" />


Moreover, since the 1960s, many disk drives used IBM's ], where each track was divided into blocks of user-specified size; and the block sizes were recorded on the disk, subtracting from the usable capacity. For example, the IBM 3336 disk pack was quoted to have a 200-megabyte capacity, achieved only with a single {{val|13030}}-byte block in each of its 808 × 19 tracks.
{{main|JEDEC memory standards}}


Decimal megabytes were used for disk capacity by the CDC in 1974.<ref name="CDC1974" /> The Seagate ],<ref name="seag1982" /> one of several types installed in the ],<ref name="CSN1984" /> had a capacity of {{val|10027008|u=bytes}} when formatted as 306 × 4 tracks and 32 256-byte sectors per track, which was quoted as "10&nbsp;MB".<ref name="mall2011" /> Similarly, a "300&nbsp;GB" hard drive can be expected to offer only slightly more than {{val|300|e=9}} = {{val|300000000000}}, bytes, not {{nowrap|300 × 2<sup>30</sup>}} (which would be about {{val|322|e=9}} bytes or "322&nbsp;GB"). The first terabyte (SI prefix, {{val|1000000000000}} bytes) hard disk drive was introduced in 2007.<ref name="hita2007" /> Decimal prefixes were generally used by information processing publications when comparing hard disk capacities.<ref name="RDD1977" />
Measurements of most types of electronic ''']''' such as ] and ] and ] (large scale disk-like flash is sometimes an exception) are given in binary units, as they are made in power-of-two sizes. This is the most natural configuration for memory, as all combinations of their address lines map to a valid address, allowing easy aggregation into a larger contiguous block of memory.


Some programs and operating systems, such as ], still use "MB" and "GB" to denote binary prefixes even when displaying disk drive capacities and file sizes, as did ]. Thus, for example, the capacity of a "10 MB" (decimal "M") disk drive could be reported as "{{nowrap|9.56 MB}}", and that of a "300&nbsp;GB" drive as "279.4&nbsp;GB". Some operating systems, such as ],<ref>{{cite web |title=How iOS and macOS report storage capacity |url=https://support.apple.com/en-us/HT201402 |website=Apple Support |access-date=9 January 2022 |language=en |date=27 February 2018 |archive-date=9 April 2020 |archive-url=https://web.archive.org/web/20200409170256/https://support.apple.com/en-us/HT201402 |url-status=live }}</ref> ],<ref>{{cite web |title=UnitsPolicy |url=https://wiki.ubuntu.com/UnitsPolicy |website=Ubuntu Wiki |publisher=Ubuntu |access-date=9 January 2022 |archive-date=18 November 2021 |archive-url=https://web.archive.org/web/20211118114902/https://wiki.ubuntu.com/UnitsPolicy |url-status=live }}</ref> and ],<ref>{{cite web |title=ConsistentUnitPrefixes |url=https://wiki.debian.org/ConsistentUnitPrefixes |website=Debian Wiki |access-date=9 January 2022 |archive-date=3 December 2021 |archive-url=https://web.archive.org/web/20211203075715/https://wiki.debian.org/ConsistentUnitPrefixes |url-status=live }}</ref> have been updated to use "MB" and "GB" to denote decimal prefixes when displaying disk drive capacities and file sizes. Some manufacturers, such as ], have released recommendations stating that properly-written software and documentation should specify clearly whether prefixes such as "K", "M", or "G" mean binary or decimal multipliers.<ref name="seaga2011" /><ref name="seag2010" />
JEDEC Solid State Technology Association, the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA) in Standard 100B.01<ref>{{Citation | last = JEDEC Solid State Technology Association
| title = Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits | journal = JESD 100B.01 | date = December 2002}}</ref> defines in the binary sense K, M and G as prefixes to units of semiconductor memory, noting that these definitions are “only included to reflect common usage” and noting that ‘IEEE/ASTM SI 10-1997 state “This practice frequently leads to confusion and is deprecated.” ’. All standards published by JEDEC are still using the common usage, including end-user packaging recommendations for memory chips.


==== Floppy disks ====
Many computer programming tasks naturally reference memory in terms of ]. For example, a 16-bit ] can reference at most 65,536 items (bytes, words, or other objects), or an operating system might map memory in terms of 4,096-byte pages, in which case exactly 8,192 pages could be allocated within 33,554,432 bytes of hardware memory. It is convenient to informally express these numbers, respectively, as 64K items, or as 8K pages of 4 Kbytes (KiB) each within 32 MBytes (MiB) of memory. A programmer can easily mentally calculate that "8K &times; 4K is 32 meg" and get it exactly right, within this powers-of-two context. This convenience is likely one source of originally adapting "kilo" and "mega" from SI as shorthand for 1,024 and 1,048,576, as specialized jargon within a segment of the industry.
] used ], and their capacities was usually specified with SI-like prefixes "K" and "M" with either decimal or binary meaning. The capacity of the disks was often specified without accounting for the internal ] overhead, leading to more irregularities.


The early 8-inch diskette formats could contain less than a megabyte with the capacities of those devices specified in kilobytes, kilobits or megabits.<ref>{{Cite web |date=2012-03-07 |title=IBM100 – The Floppy Disk |url=http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/floppy/breakthroughs/ |archive-url=https://web.archive.org/web/20120403025215/http://www-03.ibm.com/ibm/history/ibm100/us/en/icons/floppy/breakthroughs/ |url-status=dead |archive-date=3 April 2012 |access-date=2023-10-17 |website=www-03.ibm.com |language=en-US}}</ref><ref>{{cite magazine|magazine=Datamation |title=Disc Storage |date= May 1972 |pages=154, 162, 164 |quote= CDS 100 ... stores over 600 kilobits, Model 650 ... store 1.5 megabits ... }}</ref>
Almost all computer user tasks (and many high-level programming tasks) have no natural affinity or need for explicit powers of two. The consumer confusion between powers of 1000 and powers of 1024 may derive largely from some operating systems and applications that were originally written by and for programmers, and which thus reported quantities such as file sizes in familiar (to programmers) powers of 1024 while using SI (powers of 1000) abbreviations. Without such reporting, most users might not have been substantially exposed to powers of 1024, as the net memory available to users after various overheads is rarely a power of two. This legacy behavior of operating systems reporting sizes in powers of 1024 has continued to this day (in 2007) even in many GUI oriented operating systems intended mainly for non-programmers.


The 5.25-inch diskette sold with the ] could hold {{nowrap|1200 × 1024}} = {{val|1228800}} bytes, and thus was marketed as "1200&nbsp;KB" with the binary sense of "KB".<ref>{{Cite web |last=Brutman |first=Michael B. |date=July 8, 2001 |title=Working with Disks: An intro to floppy disks and floppy drives |url=http://brutmanlabs.org/Diskettes/Diskette_handling.html |website=Brutmanlabs |access-date=2024-02-19 |archive-date=2024-02-19 |archive-url=https://web.archive.org/web/20240219085221/http://brutmanlabs.org/Diskettes/Diskette_handling.html |url-status=dead }}</ref> However, the capacity was also quoted "1.2&nbsp;MB",<ref>{{Cite web |title=Floppy disk storage {{!}} IBM |url=https://www.ibm.com/history/floppy-disk#1970s+high-density+storage |access-date=2024-12-14 |website=www.ibm.com |language=en}}</ref> which was a hybrid decimal and binary notation, since the "M" meant 1000 × 1024. The precise value was {{val|1.2288|u=MB}} (decimal) or {{val|1.171875|u=MiB}} (binary).
=== Hard disk drives ===


The 5.25-inch ] had 256 bytes per sector, 13 sectors per track, 35 tracks per side, or a total capacity of {{val|116480}} bytes. It was later upgraded to 16 sectors per track, giving a total of {{nowrap|140 × 2<sup>10</sup>}} = {{val|143360}} bytes, which was described as "140KB" using the binary sense of "K".
] manufacturers state capacity in decimal units. This usage has a long tradition, even predating the ] adopted in 1960, as follows:
* The first disk drive the ] (1950s) had 5,000,000 6 bit characters organized in 100 character sectors (i.e., blocks). This predates the SI system.
* In the 1960s virtually all disk drives used IBM's variable block length format (called, Count Key Data or "CKD<ref>http://www.answers.com/topic/ckd</ref>"). Any block size could be specified up to the maximum track length. Blocks ("records" in IBM's terminology) of 88, 96, 880 and 960 were often used because they related to the fixed block size of punch cards. The drive capacity was usually stated in full track record blocking, for example, the 100 Megabyte 3336 disk pack only achieved that capacity with a full track block size of 13,030 bytes.
* CKD continued into the 1990s and perhaps into this day. In the 1970s and 1980s most drives were specified with unformatted tracks (the unformatted capacity) with the particular block size and formatted capacity a function of the controller design. For example, the ST412 of IBM PC/XT fame had an unformatted capacity of 12.75 MB (not MiB) and with the Xebec controller and 512 byte blocks it formatted to and was advertised as a 10.0 MB (not MiB) HDD. Other controllers supported other block sizes resulting in other formatted capacities.
* The advent of intelligent interfaces (] and ]) in the early 1990s took the block size decision into the drive and virtually all chose 512 bytes, for no reason other than that was what IBM had chosen when they picked the Xebec controller for the PC/XT. Capacity continued to be specified by the HDD manufacturers with SI prefix definitions.
Regardless of the HDD manufacturers' continuous practice of specifying with conventional SI prefixes, some systems' GUIs took the HDD capacity, reported by the operating system as a binary number without prefixes, and reported the HDD capacity in a mixed decimal number/binary prefix{{Fact|date=May 2007}} leading to some confusion. ], most, if not all, HDD manufacturers continue to use decimal prefixes to identify capacity.<ref>
On ] ], a check of the websites of Fujitsu, HGST, Samsung, Seagate, Toshiba and Western Digital showed these companies (representing virtually all of the HDD industry by unit volume) specify capacity with the SI prefix definitions.
</ref>


The most recent version of the physical hardware, the "3.5-inch diskette" cartridge, had 720 512-byte blocks (single-sided). Since two blocks comprised 1024 bytes, the capacity was quoted "360&nbsp;KB", with the binary sense of "K". On the other hand, the quoted capacity of "1.44&nbsp;MB" of the High Density ("HD") version was again a hybrid decimal and binary notation, since it meant 1440 pairs of 512-byte sectors, or {{nowrap|1440 × 2<sup>10</sup>}} = {{val|1474560|u=bytes}}. Some operating systems displayed the capacity of those disks using the binary sense of "MB", as "1.4&nbsp;MB" (which would be {{nowrap|1.4 × 2<sup>20</sup>}} ≈ {{val|1468000|u=bytes}}). User complaints forced both Apple{{citation needed|date=August 2023}} and Microsoft<ref name="msoftxxxx" /> to issue support bulletins explaining the discrepancy.
=== Flash drives ===
] and Flash-based memory cards like ] and ] are typically classified in "powers of two" multiples of decimal megabytes; for example, a "256 MB" card would hold 256 million bytes. Although the devices usually have at least the expected byte capacity, each manufacturer allocates different portions of the device's ultimate capacity for such things as ].


=== Floppy drives === ==== Optical disks ====
When specifying the capacities of optical ]s, "megabyte" and "MB" usually meant 1024<sup>2</sup>&nbsp;bytes. Thus a "700-MB" (or "80-minute") CD has a nominal capacity of about {{val|700|u=MiB}}, which is approximately {{val|730|u=MB}} (decimal).<ref name="cdromcap" />
The confused usage of decimal prefixes may have started in ]s where the drive and media manufacturers stated their unformatted capacity while various systems houses published differing formatted capacities as a consequence of their varying controller designs. It appears that some system manufacturers and OS vendors began reporting in what we now know as Ki bytes. A very confusing hybrid system developed with the double sided high density 3½" floppy disk, in which a "megabyte" means a thousand 1024-byte "kilobytes". Thus, ], manufacturers universally use the designation "1.44 MB ]" for a product which holds neither 1.44×2<sup>20</sup> bytes nor 1.44×10<sup>6</sup> bytes, but rather 1.44×1000×1024 bytes (approximately 1.406 MiB, or 1.475 MB).


On the other hand, capacities of other ] storage media like ], ], ] and ] have been generally specified in decimal gigabytes ("GB"), that is, 1000<sup>3</sup> bytes. In particular, a typical "{{val|4.7|u=GB}}" DVD has a nominal capacity of about {{val|4.7|e=9|u=bytes}}, which is about {{val|4.38|u=GiB}}.<ref name="dvdcap" />
=== CD and DVD ===
] capacities are always given in binary units. A "700 MB" (or "80 minute") CD has a nominal capacity of about 700 ] (approx 730MB).<ref></ref> But ''']''' capacities are given in decimal units. A "4.7 GB" DVD has a nominal capacity of about 4.38 ].<ref></ref>


=== Buses === ==== Tape drives and media ====
Tape drive and media manufacturers have generally used SI decimal prefixes to specify the maximum capacity,<ref name="IBMt2016" /><ref name="ECMA2013" /> although the actual capacity would depend on the ] used when recording.
] bandwidth is given in decimal units. This is not because hard drive capacities use the decimal versions, nor because bit rates do, but because clock speeds do. For example, "]" memory runs on a ] 200 MHz bus, transferring 8 bytes per cycle, and hence has a bandwidth of 200,000,000×2×8 = 3,200,000,000 byte/s.


==== Data and clock rates ====
==Legal disputes==
Computer ] frequencies are always quoted using SI prefixes in their decimal sense. For example, the internal clock frequency of the original ] was {{val|4.77|u=MHz}}, that is {{val|4770000|u=Hz}}.
The implicit use of decimal units to describe the capacity of storage devices has become a source of confusion as these devices are increasingly marketed to non-technical consumers. When a user buys a device advertised using decimal units, and installs it in a system that shows the available space in binary units, a misinformed user may be disturbed by the apparent discrepancy. As a result, there have been several lawsuits against companies who sell hard drives, flash memory devices, and computer systems that list drive capacities.


Similarly, digital information transfer rates are quoted using decimal prefixe. The ] "{{val|100|u=MB/s}}" disk interface can transfer {{val|100000000}} bytes per second, and a "{{val|56|u=Kb/s}}" modem transmits {{val|56000}} bits per second. Seagate specified the sustained transfer rate of some hard disk drive models with both decimal and IEC binary prefixes.<ref name="seaga2011" />
Several significant lawsuits have been filed:
The standard sampling rate of music ]s, quoted as {{val|44.1|u=kHz}}, is indeed {{val|44100}} samples per second.{{citation needed|date=August 2023}} A "{{val|1|u=Gb/s}}" ] interface can receive or transmit up to 10<sup>9</sup> bits per second, or {{val|125000000}} bytes per second within each packet. A "]" modem can encode or decode up to {{val|56000}} bits per second.


Decimal SI prefixes are also generally used for ] speeds. A ] bus with {{val|66|u=MHz}} clock and 64 bits wide can transfer {{val|66000000}} 64-bit words per second, or {{val|4224000000|u=bit/s}} = {{val|528000000|u=B/s}}, which is usually quoted as {{val|528|u=MB/s}}. A ] memory on a ] bus, transferring 8 bytes per cycle with a clock speed of {{val|200|u=MHz}} has a bandwidth of {{nowrap|{{val|200000000}} × 8 × 2}} = {{val|3200000000|u=B/s}}, which would be quoted as {{val|3.2|u=GB/s}}.
* On ], ], a Business ] action entitled Matthew Leffert vs. Amazon.com, INC., was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-03-421769. In this case, the plaintiff complained of false advertising in relation to how MP3 player storage is marketed.

** The case was dismissed on ] ].
=== Ambiguous standards ===
* In September of 2003, against ], ] Inc., ], ] Co., ] Corp., ], ] Corp. and ] Corp claiming their advertising deceptively exaggerates the real capacity of their hard drives.
The ambiguous usage of the prefixes "kilo ("K" or "k"), "mega" ("M"), and "giga" ("G"), as meaning both powers of 1000 or (in computer contexts) of 1024, has been recorded in popular dictionaries,<ref name="webster" /><ref name="metadict" /><ref name="oxford" /> and even in some obsolete standards, such as ]<ref name="ansi1986" /> and ],<ref name="ieee1992" /> ],<ref name="ieee1994" /> and ].<ref name="ieee2000" /> Some of these standards specifically limited the binary meaning to multiples of "byte" ("B") or "bit" ("b").
* On ], ], ] against Lexar Media, Dane–Elec Memory, ], ] Company, Kingston Technology Company, Inc., ] Products, Inc.; ] Inc., ], ], and Viking InterWorks alleging that their descriptions of the capacity of their ] cards were false and misleading.

* On ], ], an action entitled Orin Safier v. ] Corporation, et al., was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-05-442812. The case was subsequently moved to the Northern District of California, Case No. 05-03353 BZ.
=== Early binary prefix proposals ===
** Although Western Digital maintained that their usage of units is consistent with "the indisputably correct industry standard for measuring and describing storage capacity", and that they "cannot be expected to reform the software industry", they agreed to in March 2006 with ], ] as the Final Approval hearing date.
Before the IEC standard, several alternative proposals existed for unique binary prefixes, starting in the late 1960s. In 1996, ] proposed the extra prefix "di" and the symbol ] or ] "2" to mean "binary"; so that, for example, "one dikilobyte" would mean "1024 bytes", denoted "K<sub>2</sub>B" or "K2B".<ref name="kuhn1996" />
** Western Digital offered to compensate customers with a free download of backup and recovery software valued at US$30.

** $500,000 were paid in fees and expenses to San Francisco lawyers Adam Gutride and Seth Safier, who filed the suit.
In 1968, Donald Morrison proposed to use the Greek letter kappa (]) to denote 1024, κ<sup>2</sup> to denote 1024<sup>2</sup>, and so on.<ref name="morr1968" /> (At the time, memory size was small, and only K was in widespread use.) In the same year, ] responded with a suggestion to use bK as an abbreviation for 1024 and bK2 or bK<sup>2</sup> for 1024<sup>2</sup>, though he noted that neither the Greek letter nor lowercase letter b would be easy to reproduce on computer printers of the day.<ref name="give1968" /> ] of ] proposed that, instead of prefixes, binary powers of two were indicated by the letter ] followed by the exponent, similar to ] in ]. Thus one would write 3B20 for {{nowrap|3 × 2<sup>20</sup>}}.<ref name="mart1968" /> This convention is still used on some calculators to present binary floating point-numbers today.<ref name="schw1993" />
** Western Digital included the following footnote in the settlement: {{quote|Apparently, Plaintiff believes that he could sue an egg company for fraud for labeling a carton of 12 eggs a "dozen," because some bakers would view a "dozen" as including 13 items.|}}

In 1969, ], who uses decimal notation like 1&nbsp;MB = 1000&nbsp;kB,<ref name="knuth2016" /> proposed that the powers of 1024 be designated as "large kilobytes" and "large megabytes", with abbreviations KKB and MMB.<ref name="knuth1999" />

=== Consumer confusion ===
The ambiguous meanings of "kilo", "mega", "giga", etc., has caused significant ], especially in the ] era. A common source of confusion was the discrepancy between the capacities of hard drives specified by manufacturers, using those prefixes in the decimal sense, and the numbers reported by operating systems and other software, that used them in the binary sense, such as the ] in 1984. For example, a hard drive marketed as "1&nbsp;TB" could be reported as having only "931&nbsp;GB". The confusion was compounded by fact that RAM manufacturers used the binary sense too.

=== Legal disputes ===
The different interpretations of disk size prefixes led to class action lawsuits against digital storage manufacturers. These cases involved both flash memory and hard disk drives.

==== Early cases ====
Early cases (2004–2007) were settled prior to any court ruling with the manufacturers admitting no wrongdoing but agreeing to clarify the storage capacity of their products on the consumer packaging. Accordingly, many flash memory and hard disk manufacturers have disclosures on their packaging and web sites clarifying the formatted capacity of the devices or defining MB as 1&nbsp;million bytes and 1&nbsp;GB as 1&nbsp;billion bytes.<ref name="wdc2007" /><ref name="flash2016" /><ref name="sand2013" /><ref name="sd-cap-disclaimer" />

==== ''Willem Vroegh v. Eastman Kodak Company'' ====
On 20 February 2004, ] against Lexar Media, Dane–Elec Memory, ], ] Company, Kingston Technology Company, Inc., ] Products, Inc.; ] Inc., ], ], and ] alleging that their descriptions of the capacity of their ] cards were false and misleading.

Vroegh claimed that a 256&nbsp;MB Flash Memory Device had only 244&nbsp;MB of accessible memory. "Plaintiffs allege that Defendants marketed the memory capacity of their products by assuming that one megabyte equals one million bytes and one gigabyte equals one billion bytes." The plaintiffs wanted the defendants to use the customary values of 1024<sup>2</sup> for megabyte and 1024<sup>3</sup> for gigabyte. The plaintiffs acknowledged that the IEC and IEEE standards define a MB as one million bytes but stated that the industry has largely ignored the IEC standards.<ref name="vreo2005" />

The parties agreed that manufacturers could continue to use the decimal definition so long as the definition was added to the packaging and web sites.<ref name="sand2012" /> The consumers could apply for "a discount of ten percent off a future online purchase from Defendants' Online Stores Flash Memory Device".<ref name="safi2007" />

==== ''Orin Safier v. Western Digital Corporation'' ====
On 7 July 2005, an action entitled ''Orin Safier v. ] Corporation, et al.'' was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-05-442812. The case was subsequently moved to the Northern District of California, Case No. 05-03353 BZ.<ref name="gutr2006" />

Although Western Digital maintained that their usage of units is consistent with "the indisputably correct industry standard for measuring and describing storage capacity", and that they "cannot be expected to reform the software industry", they agreed to settle in March 2006 with 14 June 2006 as the Final Approval hearing date.<ref name="zimm2006" />

Western Digital offered to compensate customers with a ] download of backup and recovery software that they valued at US$30. They also paid {{val|p=$|500000}} in fees and expenses to San Francisco lawyers Adam Gutride and Seth Safier, who filed the suit. The settlement called for Western Digital to add a disclaimer to their later packaging and advertising.<ref name="betaxxxx" /><ref name="reim2006" /><ref name="wdc2010" />
<!--- I think that to end on this bit is overly POV. I'll leave it to someone else to add. – jeh--->
Western Digital had this footnote in their settlement. "Apparently, Plaintiff believes that he could sue an egg company for fraud for labeling a carton of 12 eggs a 'dozen', because some bakers would view a 'dozen' as including 13 items."<ref name="bask2006" />

==== ''Cho v. Seagate Technology (US) Holdings, Inc.'' ====
A lawsuit (''Cho v. Seagate Technology (US) Holdings, Inc.'', San Francisco Superior Court, Case No. CGC-06-453195) was filed against ], alleging that Seagate overrepresented the amount of usable storage by 7% on hard drives sold between 22 March 2001 and 26 September 2007. The case was settled without Seagate admitting wrongdoing, but agreeing to supply those purchasers with gratis backup software or a 5% refund on the cost of the drives.<ref name="seagb2011" />

==== ''Dinan et al. v. SanDisk LLC'' ====
On 22 January 2020, the district court of the Northern District of California ruled in favor of the defendant, SanDisk, upholding its use of "GB" to mean {{val|1000000000|u=bytes}}.<ref name="suitbxxxx" />

=== IEC 1999 Standard ===
In 1995, the ]'s (IUPAC) Interdivisional Committee on Nomenclature and Symbols (IDCNS) proposed the prefixes "kibi" (short for "kilobinary"), "mebi" ("megabinary"), "gibi" ("gigabinary") and "tebi" ("terabinary"), with respective symbols "kb", "Mb", "Gb" and "Tb",<ref name="iucr1995" /> for binary multipliers. The proposal suggested that the SI prefixes should be used only for powers of 10; so that a disk drive capacity of "500 gigabytes", "0.5 terabytes", "500&nbsp;GB", or "0.5&nbsp;TB" should all mean {{val|500|e=9|u=bytes}}, exactly or approximately, rather than {{nowrap|500 × 2<sup>30</sup>}} (=&nbsp;{{val|536870912000}}) or {{nowrap|0.5 × 2<sup>40</sup>}} (=&nbsp;{{val|549755813888}}).

The proposal was not accepted by IUPAC at the time, but was taken up in 1996 by the ] (IEEE) in collaboration with the ] (ISO) and ] (IEC). The prefixes "kibi", "mebi", "gibi" and "tebi" were retained, but with the symbols "Ki" (with capital "K"), "Mi", "Gi" and "Ti" respectively.<ref name="iucr1996" /><!-- The preceding reference is weak as it merely consists of IUPAC noting IEC's proposal, but it is apparently the only thing we have. Would be better to have a ref for the actual proposal -->

In January 1999, the IEC published this proposal, with additional prefixes "pebi" ("Pi") and "exbi" ("Ei"), as an international standard (] Amendment 2)<ref name="iec1999" /><!--- the preceding reference really needs more than just a quote. From what is it quoting? ---><ref name="iucr1999" /><!--- this reference is weak as it merely consists of the International Union of Crystallography reporting on IUPAC's reporting on the IEC standard(!) ---><ref name="IEC2000" /> The standard reaffirmed the BIPM's position that the SI prefixes should always denote powers of 10. The third edition of the standard, published in 2005, added prefixes "zebi" and "yobi", thus matching all then-defined SI prefixes with binary counterparts.<ref name="iec2005" />

The harmonized ]/] ]:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 (those defining prefixes for binary multiples). The only significant change is the addition of explicit definitions for some quantities.<ref name="niso2008" /><!--- once again, a link to a cite to the document, not to the actual ISO/IEC document. This is unavoidable as the documents in question are *not* freely available ---> In 2009, the prefixes kibi-, mebi-, etc. were defined by ] in their own right, independently of the kibibyte, mebibyte, and so on.

The BIPM standard JCGM 200:2012 "International vocabulary of metrology – Basic and general concepts and associated terms (VIM), 3rd edition" lists the IEC binary prefixes and states "SI prefixes refer strictly to powers of 10, and should not be used for powers of 2. For example, 1 kilobit should not be used to represent {{val|1024}} bits (2<sup>10</sup>&nbsp;bits), which is 1 kibibit."<ref name="jcgm2012" />

The IEC 60027-2 standard recommended operating systems and other software were updated to use binary or decimal prefixes consistently, but incorrect usage of SI prefixes for binary multiples is still common. At the time, the IEEE decided that their standards would use the prefixes "kilo", etc. with their metric definitions, but allowed the binary definitions to be used in an interim period as long as such usage was explicitly pointed out on a case-by-case basis.<ref name="barr1997" />

==== Other standards bodies and organizations ====
The IEC standard binary prefixes are supported by other standardization bodies and technical organizations.

The United States ] (NIST) supports the ISO/IEC standards for
"Prefixes for binary multiples" and has a web page<ref name="NISTbin" /> documenting them, describing and justifying their use. NIST suggests that in English, the first syllable of the name of the binary-multiple prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix, and that the second syllable should be pronounced as ''bee''.<ref name="NIST2" /> NIST has stated the SI prefixes "refer strictly to powers of 10" and that the binary definitions "should not be used" for them.<ref name="taylo2008" />

As of 2014, the microelectronics industry standards body ] describes the IEC prefixes in its online dictionary, but acknowledges that the SI prefixes and the symbols "K", "M" and "G" are still commonly used with the binary sense for memory sizes.<ref name="jedec2021" /><ref name="JEDEC2014" />

On 19 March 2005, the IEEE standard ] ("Prefixes for Binary Multiples") was elevated to a full-use standard by the IEEE Standards Association after a two-year trial period.<ref name="IEEE2003" /><ref name="IEEE2005" /> {{As of|2008|4|lc=on}}, the IEEE Publications division does not require the use of IEC prefixes in its major magazines such as ''Spectrum''<ref name="walli2008" /> or ''Computer''.<ref name ="gesch2007">{{Cite journal |last1=Gschwind |first1=Michael |title=An Open Source Environment for Cell Broadband Engine System Software |journal=Computer |volume=40 |issue=6 |pages=37–47 |publisher=IEEE Computer Society |date=June 2007 |doi = 10.1109/MC.2007.192 |last2=Erb |first2=David |last3=Manning |first3=Sid |last4=Nutter |first4=Mark |s2cid=10877922 |url=http://www.research.ibm.com/people/m/mikeg/papers/2007_ieeecomputer.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.research.ibm.com/people/m/mikeg/papers/2007_ieeecomputer.pdf |archive-date=2022-10-09 |url-status=live }} "The processor has a memory subsystem with separate first-level 32-Kbyte instruction and data caches, and a 512-Kbyte unified second-level cache." Authors are with IBM.</ref> <!-- and many of the IEEE technical journals allow the authors to select the units in their papers.{{Citation needed|date=May 2008}}-->

The ] (BIPM), which maintains the ] (SI), expressly prohibits the use of SI prefixes to denote binary multiples, and recommends the use of the IEC prefixes as an alternative since units of information are not included in the SI.<ref name="BIPM8web" /><ref name="BIPM8" />

The ] (SAE) prohibits the use of SI prefixes with anything but a power-of-1000 meaning, but does not cite the IEC binary prefixes.<ref name="SAE2017" />

The European Committee for Electrotechnical Standardization (]) adopted the IEC-recommended binary prefixes via the harmonization document HD&nbsp;60027-2:2003-03.<ref name="CENELEC2003" /> The European Union (EU) has required the use of the IEC binary prefixes since 2007.<ref name="CENELECxxxx" />

=== Current practice ===
]
]'s partition editor uses IEC prefixes to display partition sizes. The total capacity of the 120&nbsp;×&nbsp;10<sup>9</sup>-byte disk is displayed as "111.79&nbsp;GiB".]]
]

Some computer industry participants, such as Hewlett-Packard (HP),<ref name="hpen2009" /> and IBM<ref name="resp2011" /><ref name="IBMaxxxx" /> have adopted or recommended IEC binary prefixes as part of their general documentation policies.

As of 2023, the use of SI prefixes with the binary meanings is still prevalent for specifying the capacity of the ] of computers, of ], ], ], and ] ] and ]s, and of the ] of ]s. For example, a "512-megabyte" or "512&nbsp;MB" memory module holds 512&nbsp;MiB; that is, 512&nbsp;×&nbsp;2<sup>20</sup> bytes, not 512&nbsp;×&nbsp;10<sup>6</sup> bytes.<ref name="customxxxx" /><ref name="HP2012" /><ref name="sony2017" /><ref name="forall2012" />

JEDEC continues to include the customary binary definitions of "kilo", "mega", and "giga" in the document ''Terms, Definitions, and Letter Symbols'',<ref name="JEDEC-terms" /> and, {{as of|2010|lc=yes}}, still used those definitions in their ].<ref name="JEDEC-ddr3" /><ref name="JEDEC-ddr2" /><ref name="JEDEC-configs" /><ref name="JEDEC-configs-toc" /><ref name="JEDEC-configs-terms" />

On the other hand, the SI prefixes with powers of ten meanings are generally used for the capacity of external storage units, such as ],<ref name="hita2009" /><ref name="sams2011" /><ref name="seag2017" /><ref name="toshi2009" /><ref name="WDC2005" /> ], and ],<ref name="sd-cap-disclaimer" /> except for some ] chips intended to be used as ]s. However, some disk manufacturers have used the IEC prefixes to avoid confusion.<ref name="toshi2017" /> The decimal meaning of SI prefixes is usually also intended in measurements of data transfer rates, and clock speeds.{{citation needed|date=August 2023}}

Some operating systems and other software use either the IEC binary multiplier symbols ("Ki", "Mi", etc.)<ref name="linux2001" /><ref name="ESR2012" /><ref name="ubuntu2012" /><ref name="ubuntu2012b" /><ref name="snow2009" /><ref name="apple2018" /> or the SI multiplier symbols ("k", "M", "G", etc.) with decimal meaning. Some programs, such as the ] ] command, let the user choose between binary or decimal multipliers. However, some continue to use the SI symbols with the binary meanings, even when reporting disk or file sizes. Some programs may also use "K" instead of "k", with either meaning.<ref>{{cite web | url=https://man7.org/linux/man-pages/man1/ls.1.html | title=Ls(1) – Linux manual page }}</ref>

== Other uses ==
While the binary prefixes are almost always used with the units of information, bits and bytes, they may be used with any other unit of measure, when convenient. For example, in ] one may need binary multiples of the frequency unit ] (Hz), for example the ] (KiHz), equal to {{val|1024|u=Hz}}.<ref name="pate2011" /><ref name="ains2022" />


== See also == == See also ==
* ] * ]
* ]
* ]
* ]
* ] * ]
* ]
* ] * ]
* ]
* ]
* ]

=== Specific units of IEC 60027-2 A.2 ===
These units have individual articles:

{| style="float:left;"
|{{Bitrates}}
|}
{| style="float:left;"
|{{Quantities of bytes}}
|}
{| style="float:left;"
|{{Quantities of bits}}
|}
{{clear}} {{clear}}


== References == == References ==
{{reflist|refs=
<references />

<ref name="hpen2009">Hewlett-Packard (2009): ISS Technology Update – Hewlett Packard Enterprise, volume 9, issue 1, quote: 'To reduce confusion, vendors are pursuing one of two remedies: they are changing SI prefixes to the new binary prefixes, or they are recalculating the numbers as powers of ten. HP is considering modifying its storage utilities to report disk capacity with correct decimal and binary values side-by-side (for example, "300&nbsp;GB (279.4&nbsp;GiB)"), and report cache sizes with binary prefixes ("1&nbsp;GiB")'.</ref>

<ref name="suitxxxx">{{cite web | url = https://www.courthousenews.com/wp-content/uploads/2020/01/flashdrives.pdf | title = Order Granting Motion to Dismiss | publisher = ] | access-date = 2020-01-24 }}</ref>

<ref name="sand2021">See also Dinan v. SanDisk LLC, No. 20-15287 (9th Cir. Feb. 11, 2021) https://scholar.google.com/scholar_case?case=16989791406584358656</ref>

<ref name="NIST1">{{cite web | url=http://physics.nist.gov/cuu/Units/prefixes.html | title = SI prefixes |author=<!--Not stated--> | website = The NIST Reference on Constants, Units, and Uncertainty: International System of Units (SI) | date = 13 January 2010 | publisher = ] | access-date = 2017-04-03}}</ref>

<ref name="frev1795">{{cite web |title=La Loi Du 18 Germinal An 3: Décision de tracer le mètre, unité fondamentale, sur une règle de platine. Nomenclature des " mesures républicaines ". Reprise de la triangulation. |language=fr |trans-title=The Law of 18 ], Year 3: Decision to draw the fundamental unit metre on a platinum ruler. Nomenclature of "Republican measures". Resumption of the triangulation. |work=L'Histoire Du Mètre |publisher=histoire.du.metre.free.fr |url=http://histoire.du.metre.free.fr/fr/Pages/Sommaire/06.htm |access-date=2015-10-12 |url-status=live |archive-url=https://web.archive.org/web/20221126164814/http://histoire.du.metre.free.fr/fr/Pages/Sommaire/06.htm |archive-date=2022-11-26 |quote=Art. 8. Dans les poids et mesures de capacité, chacune des mesures décimales de ces deux genres aura son double et sa moitié, afin de donner à la vente des divers objets toute la commodité que l'on peut désirer. Il y aura donc le double-litre et le demi-litre, le double-hectogramme et le demi-hectogramme, et ainsi des autres. |trans-quote=Art. 8. In the weights and measures of capacity, each of the decimal measures of these two kinds will have its double and its half, in order to give to the sale of the various articles all the convenience that one can desire. There will therefore be the double-litre and the half-litre, the double-hectogram and the half-hectogram, and so on.}}</ref>

<ref name="weik1961">{{cite journal |title = A Third Survey of Domestic Electronic Digital Computing Systems: Chapter III Analysis and Trends |quote = Of 187 different relevant systems, 131 utilize a straight binary system internally, whereas 53 utilize the decimal system (primarily binary coded decimal) and 3 systems utilize a binary coded alphanumeric system of notation. |journal = Ballistic Research Laboratories Report No. 1115 | first = Martin H. |last = Weik |date=March 1961 |page = 1027 |url = http://ed-thelen.org/comp-hist/BRL61analysis.html#STORAGE }} This lengthy report describes many of the early computers.</ref>

<ref name="blais1930">Hunting Trouble on 28 Megacycles, A. L. Blais, QST, January 1930.</ref>

<ref name="real1959">{{Cite journal | last = Real | first = P. | title = A generalized analysis of variance program utilizing binary logic. | journal = ACM '59: Preprints of Papers Presented at the 14th National Meeting of the Association for Computing Machinery | pages = 78–1–78–5 |date=September 1959 | doi = 10.1145/612201.612294 | publisher = ACM Press | s2cid = 14701651 | quote = On a 32K core size 704 computer, approximately {{val|28000}} data may be analyzed, ... without resorting to auxiliary tape storage.| doi-access = free }} Note: the IBM 704 core memory units had 4096 36-bit words. Up to {{val|32768}} words could be installed</ref>

<ref name="gruen1960">{{Cite journal | last1 =Gruenberger | first1 =Fred | title =Letters to the Editor | journal =Communications of the ACM | volume =3 | issue =10 |date=October 1960 | doi = 10.1145/367415.367419 | last2 =Burgess | first2 =C. R. | last3 =Gruenberger | first3 =Fred| s2cid =3199685 }} "The 8K core stores were getting fairly common in this country in 1954. The 32K store started mass production in 1956; it is the standard now for large machines and at least 200 machines of the size (or its equivalent in the character addressable machines) are in existence today (and at least 100 were in existence in mid-1959)." Note: The ] was a character addressable computer.</ref>

<ref name="amda1964">{{Cite journal | last =Amdahl | first = Gene M. | author-link = Gene Amdahl | title = Architecture of the IBM System/360 | journal =IBM Journal of Research and Development | volume =8 | issue =2 | publisher = IBM | year = 1964 | url = http://www.research.ibm.com/journal/rd/441/amdahl.pdf | doi = 10.1147/rd.82.0087 | pages=87–101}} Figure 1 gives storage (memory) capacity ranges of the various models in "Capacity 8-bit bytes, 1 K = 1024"</ref>

<ref name="CDC7600">{{Cite book | author = Control Data Corporation | title = Control Data 7600 Computer System: Preliminary System Description |date=November 1968 | url = http://archive.computerhistory.org/resources/text/CDC/CDC.7600.1968.102646087.pdf |quote = One type, designated as the small core memory (SCM) is a many bank coincident current type memory with a total of 64K words of 60 bit length (K=1024). }}</ref>

<ref name="CDC1967">{{Cite book |author = Control Data Corporation |title = Control Data 6400/6500/6600 Computer Systems Reference Manual |year = 1965–1967 |pages = 2–1 |edition = Pub No. 60100000 |url = http://ed-thelen.org/comp-hist/CDC-6600-R-M.html#TOC/ |quote = Central Memory is organized into 32K, 65K, or 131K words (60-bit) in 8, 16, or 32 banks of 4096 words each. |access-date = 2013-11-07 |archive-url = https://web.archive.org/web/20140102194752/http://ed-thelen.org/comp-hist/CDC-6600-R-M.html#TOC/ |archive-date = 2014-01-02 }}</ref>

<ref name="frank1974">{{Cite journal |last = Frankenberg |first = Robert |title = All Semiconductor Memory Selected for New Minicomputer Series |journal = Hewlett-Packard Journal |volume = 26 |issue = 2 |pages = 15–20 |publisher = Hewlett-Packard |date = October 1974 |url = http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1974-10.pdf |access-date = 2007-06-18 |quote = 196K-word memory size |archive-date = 2007-11-29 |archive-url = https://web.archive.org/web/20071129060208/http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1974-10.pdf |url-status = dead }}</ref>

<ref name="HP1973">{{Cite journal | last = Hewlett-Packard | title =HP 3000 Configuration Guide | journal = HP 3000 Computer System and Subsystem Data | page = 59 |date = November 1973 | url = http://www.bitsavers.org/pdf/hp/3000/hp3000/5952-4500_optionsBrochure_Nov73.pdf |access-date=2010-01-22}}</ref>

<ref name="horak2008">{{cite book|title=Webster's New World Telecom Dictionary|author=Ray Horak|page=271|publisher=]|year=2008|isbn=9780471774570|quote=In computing and storage systems, a kB (kiloByte) is actually 1,024 (2^10) bytes, since the measurement is based on a base 2, or binary, number system. The term kB comes from the fact that 1,024 is nominally, or approximately, 1,000.}}</ref>

<ref name="dodd1997">{{cite book |title=The ACS style guide: a manual for authors and editors|author=Janet S. Dodd|page=124|publisher=]|year=1997|isbn=9780841234611|quote=kB (kilobyte; actually 1024 bytes) KB (kilobyte; kB is preferred)}}</ref>

<ref name="laver1989">{{cite book |title=Information Technology: Agent of Change|author=F. J. M. Laver|date=11 May 1989|page=35|publisher=]|isbn=978-0521350358|quote=when describing the performance of IT systems the larger units 'kilobytes' (kB) Strictly speaking, k means the 'binary thousand' 1024}}</ref>

<ref name="liny1972">{{Cite journal|last1=Lin |first1=Yeong |title=Cost-performance evaluation of memory hierarchies |journal=IEEE Transactions on Magnetics |volume=8 |issue=3 |pages=390–392 |publisher=IEEE |date=September 1972 |quote=Also, random access devices are advantageous over serial access devices for backing store applications only when the memory capacity is less than 1&nbsp;Mbyte. For capacities of 4&nbsp;Mbyte and 16&nbsp;Mbyte serial access stores with shift register lengths of 256 bit and 1024 bit, respectively, look favorable. |doi=10.1109/TMAG.1972.1067329 |last2=Mattson |first2=R. |bibcode=1972ITM.....8..390L}}</ref>

<ref name="IBM1972">{{Cite book | last =IBM| title = System/370 Model 158 brochure | publisher = IBM | year = 1972 | url = http://archive.computerhistory.org/resources/text/IBM/IBM.370Mod158.1972.102646258.pdf | quote = All-monolithic storage ... (1024-bit NMOS) This new improvement of processor storage makes system expansion more economical. Real storage capacity is available in 512K increments ranging from 512K to 2,048K bytes. | id = G520-261871 }}</ref>

<ref name="bell1975">{{Cite journal | last = Bell | first = Gordon | title = Computer structures: What have we learned from the PDP-11? | journal = ISCA '76: Proceedings of the 3rd Annual Symposium on Computer Architecture | pages = 1–14 | publisher = ACM Press |date=November 1975 | url = http://research.microsoft.com/~gbell/Digital/Bell_Strecker_What_we%20_learned_fm_PDP-11c%207511.pdf | doi = 10.1145/800110.803541 | s2cid = 14496112 | quote = memory size (8k bytes to 4 megabytes). }}</ref>

<ref name="IBM1956">{{cite web |url=http://www-03.ibm.com/ibm/history/exhibits/storage/storage_350.html |archive-url=https://web.archive.org/web/20050409064858/http://www-03.ibm.com/ibm/history/exhibits/storage/storage_350.html |url-status=dead |archive-date=9 April 2005 |work=IBM Archives |title=IBM 350 disk storage unit |author=IBM Corporation|date=23 January 2003 }}</ref>

<ref name="CDC1974">The unambiguously uses MB to characterize HDD capacity in millions of bytes</ref>

<ref name="RDD1977">1977 Disk/Trend Report – Rigid Disk Drives, published June 1977</ref>

<ref name="seag1982">{{cite book |url = http://maben.homeip.net/static/S100/seagate/disks/Seagate%20ST412%20OEM%20Manual%201982.pdf |title = ST506/412 OEM Manual |author = Seagate Corporation |date = April 1982 |page = 3 |access-date = 2016-09-06 |archive-url = https://web.archive.org/web/20161008003923/http://maben.homeip.net/static/S100/seagate/disks/Seagate%20ST412%20OEM%20Manual%201982.pdf |archive-date = 2016-10-08 }}</ref>

<ref name="CSN1984">IBM Tells MiniScribe It Is Cutting Back On Winchester Orders, Computer System News, 1 Jan 1984, p. 1</ref>

<ref name="mall2011">{{cite web|last=Mellor |first=Chris |url=https://www.theregister.co.uk/2011/04/06/oldest_seagate_drive_in_uk/ |title=It's the oldest working Seagate drive in the UK |publisher=The Register |date=2011-04-06 |access-date=2012-01-26}}</ref>

<ref name="seaga2011">, 100628561, Rev D, March 2011, sec 5.2.3, p. 10 (18th page of the pdf), states the drive's sustained transfer speed as "89 to 160 ]/s" on one line, and "93 to 168&nbsp;MB/s" on the next line.</ref>

<ref name="seag2010">{{cite web|title=Marketing Bulletin: Advanced Format 4K Sector Transition Frequently Asked Questions|url=http://www.seagate.com/docs/pdf/whitepaper/mb604_4k_transition_faq.pdf|publisher=]|archive-url=https://web.archive.org/web/20100715030704/http://www.seagate.com/docs/pdf/whitepaper/mb604_4k_transition_faq.pdf|archive-date=15 July 2010}}</ref>

<ref name="hita2007">{{cite web |url=http://www.pcworld.com/article/id,128400-page,1/article.html |title=Hitachi Introduces 1-Terabyte Hard Drive |work=PC World |date=2007-01-04 |access-date=2010-02-04 |archive-date=2007-01-12 |archive-url=https://web.archive.org/web/20070112044932/http://www.pcworld.com/article/id,128400-page,1/article.html }}</ref>

<ref name="ansi1986">{{Cite book|date=30 October 1986 |quote=kilo (K). (1) A prefix indicating 1000. (2) In statements involving size of computer storage, a prefix indicating 2<sup>10</sup>, or 1024. mega (M). (1) A prefix indicating one million. (2) In statements involving size of computer storage, a prefix indicating 2<sup>20</sup>, or 1048576. |doi=10.1109/IEEESTD.1986.79649 |isbn=0-7381-4541-6 |title=IEEE Standard Glossary of Mathematics of Computing Terminology }}</ref>

<ref name="ieee1992">{{Cite book|date=22 July 1992 |quote=Kbyte. Kilobyte. Indicates 2<sup>10</sup> bytes. Mbyte. Megabyte. Indicates 2<sup>20</sup>bytes. Gbyte is used in the Foreword. |doi=10.1109/IEEESTD.1992.106981 |isbn=0-7381-4336-7 |title=IEEE Standard Control and Status Register (CSR) Architecture for Microcomputer Buses }}</ref>

<ref name="webster">{{cite web|url=http://www.m-w.com/dictionary/Megabyte|title=Definition of megabyte|website=M-w.com|access-date=30 December 2017}}</ref>

<ref name="metadict">{{cite web|url=http://dictionary.reference.com/browse/Megabyte|title=Definitions of Megabyte|website=Dictionary.reference.com|access-date=30 December 2017}}</ref>

<ref name="oxford">{{cite web|url=http://www.askoxford.com/concise_oed/megabyte?view=uk|archive-url=https://web.archive.org/web/20050525164142/http://www.askoxford.com/concise_oed/megabyte?view=uk|url-status=dead|archive-date=25 May 2005|title=AskOxford: megabyte|website=Askoxford.com|access-date=30 December 2017}}</ref>

<ref name="ieee1994">{{Cite book | date=24 June 1994 | quote= gigabyte (gig, GB). This term may mean either a) {{val|1000000000}} bytes or b) 2<sup>30</sup> bytes. ... As used in this document, the terms kilobyte (kB) means 2<sup>10</sup> or 1024 bytes, megabyte (MB) means 1024 kilobytes, and gigabyte (GB) means 1024 megabytes.|doi=10.1109/IEEESTD.1995.79522 |isbn=1-55937-492-6 | title=IEEE Standard Glossary of Computer Hardware Terminology }}</ref>

<ref name="ieee2000">{{Cite book|author=Institute of Electrical and Electronics Engineers |title=100-2000 |author-link=Institute of Electrical and Electronics Engineers |publisher=IEEE Computer Society Press |year=2000 |isbn=978-0-7381-2601-2 |doi=10.1109/IEEESTD.2000.322230 |url=https://repositorio.unal.edu.co/handle/unal/79391 }} "kB See kilobyte." "Kbyte Kilobyte. Indicates 2<sup>10</sup> bytes." "Kilobyte Either 1000 or 2<sup>10</sup> or 1024 bytes." The standard also defines megabyte and gigabyte with a note that an alternative notation for base 2 is under development.</ref>

<ref name="wdc2007">{{cite web | url = http://www.wdc.com/en/products/Products.asp?DriveID=301 | title = WD Caviar SE16 SATA Hard Drives | work = Western Digital: Products | publisher = ] | access-date = 2007-09-09 | archive-url = https://web.archive.org/web/20070902080558/http://www.wdc.com/en/products/products.asp?driveid=301 | archive-date = 2007-09-02 }}</ref>

<ref name="flash2016">{{cite web | url = http://forum.corsair.com/v3/showthread.php?t=33071 | title = Jack Flash F.A.Q. | publisher = ] | access-date = 2014-06-20 | quote = the industry-standard definition of a megabyte (MByte) for flash devices is one million (1,000,000) bytes, where the operating system uses two to the twentieth power, or 1,048,576 bytes. Similarly, for a gigabyte (GByte), the number is 1,000,000,000 and 1,073,741,824 respectively. | archive-date = 2016-03-05 | archive-url = https://web.archive.org/web/20160305080304/http://forum.corsair.com/v3/showthread.php?t=33071 }}</ref>

<ref name="sand2013">{{cite web |url=http://www.sandisk.com/media/416788/80-11-01707_rev1_datasheet_ultracf_r1.pdf |title=SanDisk Ultra CompactFlash cards |publisher=] |access-date=2014-06-20 |archive-url=https://web.archive.org/web/20130810032314/http://www.sandisk.com/media/416788/80-11-01707_rev1_datasheet_ultracf_r1.pdf |archive-date=2013-08-10 }}</ref>

<ref name="vreo2005">{{cite web|date=10 March 2005 |url=https://www.pddocs.com/FlashMemory/Documents/Vroegh%20Third%20Amended%20Complaint.pdf |title=Vreogh Third Amended Complaint (Case No. GCG-04-428953) |work=pddocs.com |publisher=Poorman-Douglas Corporation |access-date=2007-09-09 |archive-url=https://web.archive.org/web/20080309143513/https://www.pddocs.com/FlashMemory/Documents/Vroegh%20Third%20Amended%20Complaint.pdf |archive-date=9 March 2008 }}</ref>

<ref name="sand2012">{{cite web |title=Why is the capacity of my Secure Digital memory card (as reported by many operating systems) different than the capacity that is listed on its label? |url=http://www.sandisk.com/Assets/Categories/Products/sd_capacitydisclaimer.pdf|archive-url=https://web.archive.org/web/20120413100902/http://www.sandisk.com/Assets/Categories/Products/sd_capacitydisclaimer.pdf|archive-date=13 April 2012|date=13 April 2012|website=Sandisk.com|access-date=30 December 2017}}</ref>

<ref name="safi2007">{{cite web|last=Safier |first=Seth A. |url=https://www.pddocs.com/FlashMemory/faq.aspx |title=Frequently Asked Questions |work=Flash Memory Settlement |publisher=Poorman-Douglas Corporation |access-date=2007-09-09 |archive-url=https://web.archive.org/web/20070928013731/https://www.pddocs.com/FlashMemory/faq.aspx |archive-date=28 September 2007 }}</ref>

<ref name="gutr2006">{{cite web | last = Gutride | first = Adam | author2 = Seth A. Safier | date = 29 March 2006 | url = http://www.wdc.com/settlement/docs/complaint.htm | title = Class Action Complaint | work = Orin Safier v. Western Digital Corporation | publisher = ] | access-date = 2007-09-09 | archive-url = https://web.archive.org/web/20071016171124/http://wdc.com/settlement/docs/complaint.htm | archive-date = 16 October 2007 }}</ref>

<ref name="zimm2006">{{cite web | last = Zimmerman | first = Bernard | year = 2006 | url = http://www.wdc.com/settlement/docs/longform.htm | title = Notice of Class Action and Proposed Settlement | work = Orin Safier v. Western Digital Corporation | publisher = ] | access-date = 2007-09-09 | archive-url = https://web.archive.org/web/20070922234210/http://www.wdc.com/settlement/docs/longform.htm | archive-date = 2007-09-22 }}</ref>

<ref name="betaxxxx">{{cite web|url=http://www.betanews.com/article/Western_Digital_Settles_Capacity_Suit/1151510648|title=Western Digital Settles Capacity Suit|website=Betanews.com|access-date=30 December 2017|date=28 June 2006}}</ref>

<ref name="reim2006">{{cite web |url=https://arstechnica.com/old/content/2006/06/7174.ars |title=Western Digital settles drive size lawsuit |author=Jeremy Reimer |date=2006-06-30 |publisher=Ars Technica LLC |access-date=2010-02-10 }}</ref>

<ref name="wdc2010">{{cite web |url=http://www.wdc.com/settlement/docs/longform.htm |title=NOTICE OF CLASS ACTION AND PROPOSED SETTLEMENT ("NOTICE") |author=Western Digital Corporation |year=2006 |access-date=2010-02-10 |archive-url=https://web.archive.org/web/20100507132711/http://www.wdc.com/settlement/docs/longform.htm |archive-date=2010-05-07 }}</ref>

<ref name="bask2006">{{cite web | last = Baskin | first = Scott D. | date = 1 February 2006 | url = http://www.wdc.com/settlement/docs/document20.htm | title = "Defendant Western Digital Corporation's Brief in Support of Plaintiff's Motion for Preliminary Approval" | work = Orin Safier v. Western Digital Corporation | publisher = ] | access-date = 2007-09-09 }}</ref>

<ref name="seagb2011">{{cite web | url = http://www.harddrive-settlement.com | title = Settlement Website for Cho v. Seagate Technology (US) Holdings, Inc. | access-date = 2011-04-12 | archive-url = https://web.archive.org/web/20190118155341/http://www.harddrive-settlement.com/ | archive-date = 18 January 2019 }}</ref>

<ref name="suitbxxxx">{{cite web | url = https://www.courthousenews.com/wp-content/uploads/2020/01/flashdrives.pdf | title = Order Granting Motion to Dismiss | publisher = ] | access-date = 2020-01-24 }}</ref>

<ref name="morr1968">{{Cite journal |title=Letters to the editor: Abbreviations for computer and memory sizes |author= Donald R. Morrison, ] |journal= Communications of the ACM |volume=11 |issue=3 |date=March 1968 |page=150 |doi=10.1145/362929.362962|s2cid= 22934466 |doi-access=free}}</ref>

<ref name="give1968">{{Cite journal |title=Letters to the editor: proposed abbreviation for 1024: bK |author= Wallace Givens, Applied National Lab |journal= Communications of the ACM |volume=11 |issue=6 |date=June 1968 |page=391 |doi=10.1145/363347.363351|s2cid= 22205692 |doi-access=free}}</ref>

<ref name="mart1968">{{cite journal | title=Letters to the editor: On binary notation | first=Bruce Alan | last=Martin | publisher=] | journal=] | volume=11 | issue=10 | date=October 1968 | page=658 | doi=10.1145/364096.364107| s2cid=28248410 | doi-access=free }}</ref>

<ref name="schw1993">{{cite book|title=HP16C Emulator Library for the HP48S/SX|first1=Jake|last1=Schwartz|first2=Rick|last2=Grevelle|date=2003-10-20|orig-date=1993<!-- 1993-04 -->|edition=1|version=1.20|url=http://www.pahhc.org/mul8r.htm|access-date=2015-08-15}}</ref>

<ref name="kuhn1996">{{cite web |url=http://www.cl.cam.ac.uk/~mgk25/information-units.txt |title=Standardized units for use in information technology |author-first=Markus |author-last=Kuhn|author-link=Markus Kuhn (computer scientist) |date=29 December 1996}}</ref>

<ref name="knuth2016">'' {{webarchive|url=https://web.archive.org/web/20160305014709/http://www-cs-staff.stanford.edu/~knuth/fasc1.ps.gz |date=2016-03-05 }}'' Volume 1, ], pp. 24 and 94</ref>

<ref name="knuth1999">{{cite web|url=https://www-cs-faculty.stanford.edu/~knuth/news99.html |title=Knuth: Recent News (1999) |publisher=Cs-staff.stanford.edu |access-date=2012-01-26}}</ref>

<ref name="iucr1995">{{cite web |title=IUCr annual report for 1995 |publisher=] |author=IUCr IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS) |type=Report |date=1997-02-13 |orig-date=1995 |url=http://ww1.iucr.org/cexec/rep95/idcns.htm |access-date=2012-01-26 |url-status=dead |archive-url=https://web.archive.org/web/20090827091437/http://ww1.iucr.org/cexec/rep95/idcns.htm |archive-date=2009-08-27}}</ref>

<ref name="iucr1996">{{cite web |title=(IUCr) 1996 Report – IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS) |type=Report |publisher=] |date=1997-02-14 |orig-date=1996 |url=http://www.chester.iucr.org/iucr-top/cexec/rep96/idcns.htm |access-date=2012-01-26 |url-status=dead |archive-url=https://web.archive.org/web/20130613121942/http://www.chester.iucr.org/iucr-top/cexec/rep96/idcns.htm |archive-date=2013-06-13}}</ref>

<ref name="barr1997">{{cite journal |author-first=Bruce |author-last=Barrow |title=A Lesson in Megabytes |journal=IEEE Standards Bearer |volume=11 |date=January 1997 |orig-date=1996 |publisher=] |page=5 |url=https://www.thierry-lequeu.fr/data/PELS/Comm/Publications/Newsletter/9704/STORY18.HTML |access-date=2022-12-24 |url-status=live |archive-url=https://web.archive.org/web/20220528124411/https://www.thierry-lequeu.fr/data/PELS/Comm/Publications/Newsletter/9704/STORY18.HTML |archive-date=2022-05-28}}</ref>

<ref name="iec1999">"These prefixes for binary multiples, which were developed by IEC Technical Committee (TC) 25, Quantities and units, and their letter symbols, with the strong support of the International Committee for Weights and Measures (CIPM) and the IEEE, were adopted by the IEC as Amendment 2 to IEC International Standard IEC 60027-2: Letter symbols to be used in electrical technology – Part 2: Telecommunications and electronics."</ref>

<ref name="iucr1999">{{cite journal|url=http://journals.iucr.org/a/issues/2000/06/00/es0288/es0288bdy.html#SEC15.1 |title=IUCR 1999 report on IUPAC Interdivisional Committee on Nomenclature and Symbols |journal=Acta Crystallographica Section A: Foundations of Crystallography |date=November 2000 |volume=56 |issue=6 |pages=609–642 |publisher=Journals.iucr.org |doi=10.1107/S0108767300012873 |pmid=11058849 |access-date=2012-01-26|doi-access=free }}</ref>

<ref name="IEC2000">IEC 60027-2 (2000-11) Ed. 2.0</ref>

<ref name="iec2005">{{cite press release|date=2005-08-15 |title=HERE COME ZEBI AND YOBI |publisher=International Electrotechnical Commission |url=http://www.iec.ch/news_centre/release/nr2005/nr2005.htm |archive-url=https://archive.today/20070611071833/http://www.iec.ch/news_centre/release/nr2005/nr2005.htm |archive-date=11 June 2007 }}</ref>

<ref name="niso2008">{{cite web |url=http://www.niso.org/publications/newsline/2008/newslinemay2008.htm#Spec4 |title=niso, New Specs and Standards |publisher=Niso.org |access-date=2012-01-26 |archive-url=https://web.archive.org/web/20081208131408/http://www.niso.org/publications/newsline/2008/newslinemay2008.htm#Spec4 |archive-date=2008-12-08 }}</ref>

<ref name="jcgm2012">{{cite web|url=http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf |archive-date=2022-10-09 |url-status=live|title=International vocabulary of metrology – Basic and general concepts and associated terms (VIM)|edition=3rd|website=Bipm.org|access-date=30 December 2017}}</ref>

<ref name="BIPM2022">{{cite web |title=List of Resolutions for the 27th meeting of the General Conference on Weights and Measures |url=https://www.bipm.org/documents/20126/64811223/Resolutions-2022.pdf |archive-url=https://web.archive.org/web/20221118153958/https://www.bipm.org/documents/20126/64811223/Resolutions-2022.pdf |archive-date=2022-11-18 |url-status=live |date=2022-11-18 |access-date=2022-11-18 }}</ref>

<ref name="gibn2022">{{cite journal |title=How many yottabytes in a quettabyte? Extreme numbers get new names |author-last=Gibney |author-first=Elizabeth |date=2022-11-18 |journal=] |volume= |issue= |pages= |doi=10.1038/d41586-022-03747-9 |pmid=36400954 |s2cid=253671538 |url=https://www.nature.com/articles/d41586-022-03747-9 |access-date=2022-11-21}}</ref>

<ref name="brown2023">{{cite journal |title=A further short history of the SI prefixes |journal=] |department=Letter to the editor |author-first=Richard J. C. |author-last=Brown |date=2023 |orig-date=2022-02-08, 2022-04-01, 2022-11-24 |volume=60 |issue=1 |page=013001 |publisher=] & ] |id=013001 |doi=10.1088/1681-7575/ac6afd |bibcode=2023Metro..60a3001B |s2cid=253966045 |doi-access=free }} (1+4 pages)</ref>

<ref name="brown2022">{{cite journal |title=Reply to 'Facing a shortage of the Latin letters for the prospective new SI symbols: alternative proposal for the new SI prefixes' |author-last=Brown |author-first=Richard J. C. |date=2022-04-27 |journal={{ill|Accreditation and Quality Assurance|de}} |volume=27 |issue= 3|pages=143–144 |doi=10.1007/s00769-022-01499-7|s2cid=248397680 }}</ref>

<ref name="NISTbin"></ref>

<ref name="NIST2">{{cite web | url = http://physics.nist.gov/cuu/Units/binary.html | title = International System of Units (SI): Prefixes for binary multiples | work = The NIST Reference on Constants, Units, and Uncertainty | publisher = ] | access-date = 2007-09-09 }}</ref>

<ref name="taylo2008">{{Cite book |author=Barry N. Taylor & Ambler Thompson Ed. |title=The International System of Units (SI) |url=http://physics.nist.gov/Pubs/SP330/sp330.pdf |access-date=2010-04-27 |publisher=National Institute of Standards and Technology |location=Gaithersburg, MD |page=29 |year=2008 |archive-date=2018-12-25 |archive-url=https://web.archive.org/web/20181225010952/https://physics.nist.gov/Pubs/SP330/sp330.pdf }}</ref>

<ref name="jedec2021">{{cite web|title=mega (M) (as a prefix to units of semiconductor storage capacity)|url=http://www.jedec.org/standards-documents/dictionary/terms/mega-m-prefix-units-semiconductor-storage-capacity|website=JEDEC – Global Standards for the Microelectronics Industry|access-date=14 April 2021|quote = "The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage."}}</ref>

<ref name="JEDEC2014">{{cite book | title = Low Power Double Data Rate 4 (LPDDR4) JESD209-4 | publisher = JEDEC Solid State Technology Association | date = August 2014 | page = 7 | url = http://www.jedec.org/standards-documents/results/jesd79-4%20ddr4 | quote = These devices contain the following number of bits: 4Gb has 4,294,967,296 bits ... 32Gb has 34,359,738,368 bits}} Free registration required to download the standard.</ref>

<ref name="IEEE2003">{{Cite book|doi=10.1109/IEEESTD.2003.94236 |url=http://ieeexplore.ieee.org/servlet/opac?punumber=8450 |archive-url=https://web.archive.org/web/20121014151530/http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?reload=true&punumber=8450 |archive-date=2012-10-14 |access-date=2007-07-29 |date=12 February 2003 |version=Reaffirmed 27 March 2008 |quote=This standard is prepared with two goals in mind: (1) to preserve the SI prefixes as unambiguous decimal multipliers and (2) to provide alternative prefixes for those cases where binary multipliers are needed. The first goal affects the general public, the wide audience of technical and nontechnical persons who use computers without much concern for their construction or inner working. These persons will normally interpret kilo, mega, etc., in their proper decimal sense. The second goal speaks to specialists – the prefixes for binary multiples make it possible for persons who work in the information sciences to communicate with precision. |isbn=978-0-7381-3385-0 |title=1541-2002 }}</ref>

<ref name="IEEE2005">{{cite web|url=http://standards.ieee.org/board/rev/305agenda.html |title=IEEE-SA Standards Board Standards Review Committee (RevCom) Meeting Agenda |access-date=2007-02-25 |date=2005-03-19 |quote='''1541-2002''' (SCC14) IEEE Trial-Use Standard for Prefixes for Binary Multiples '''' <u>Recommendation</u>: Elevate status of standard from trial-use to full-use. Editorial staff will be notified to implement the necessary changes. The standard will be due for a maintenance action in 2007. |archive-url=https://web.archive.org/web/20070922215418/http://standards.ieee.org/board/rev/305agenda.html |archive-date=22 September 2007 }}</ref>

<ref name="walli2008">{{Cite journal |last=Wallich |first=Paul |title=Tools & toys: Hacking the Nokia N800 |journal=IEEE Spectrum |volume=45 |issue=4 |page=25 |date=April 2008 |doi=10.1109/MSPEC.2008.4476441 |s2cid=20129812 }} ''"A lot can happen in a decade. You can hold the Nokia N800 in your hand, yet it's a near-exact match for a high-end desktop PC from 10 years ago. It has a 320-megahertz processor, 128 megabytes of RAM, and a few gigabytes of available mass storage."''</ref>

<ref name="BIPM8web">{{cite web |url=http://www.bipm.org/en/si/prefixes.html |title=BIPM – SI prefixes|website=Bipm.org|access-date=30 December 2017}}</ref>

<ref name="BIPM8">{{Cite book |title=The International System of Units (SI) |chapter-url=http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf |archive-url=https://web.archive.org/web/20060813144253/http://www.bipm.org/utils/common/pdf/si_brochure_8.pdf |archive-date=2006-08-13 |url-status=live |access-date=2007-02-25 |edition=8th |year=2006 |publisher=STEDI Media |location=Paris |language=fr, en |isbn=978-92-822-2213-3 |page=127 |chapter=§3.1 SI prefixes |quote= These SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The IEC has adopted prefixes for binary powers in the international standard IEC 60027-2: 2005, third edition, ''Letter symbols to be used in electrical technology – Part 2: Telecommunications and electronics''. The names and symbols for the prefixes corresponding to 2<sup>10</sup>, 2<sup>20</sup>, 2<sup>30</sup>, 2<sup>40</sup>, 2<sup>50</sup>, and 2<sup>60</sup> are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1&nbsp;KiB = 2<sup>10</sup>&nbsp;B = 1024&nbsp;B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes. |author=Bureau International des Poids et Mesures.}}</ref>

<ref name="SAE2017">{{cite web|url=http://www.sae.org/standardsdev/tsb/tsb003.pdf#page=33 |archive-url=https://ghostarchive.org/archive/20221009/http://www.sae.org/standardsdev/tsb/tsb003.pdf#page=33 |archive-date=2022-10-09 |url-status=live|format=PDF|title=Rules for SAE Use of SI (Metric) Units] – Section C.1.12 – SI prefixes|website=Sae.org|access-date=30 December 2017}}</ref>

<ref name="CENELEC2003">{{Cite web|url=http://www.cenelec.eu/dyn/www/f?p=104:110:1546953662480229::::FSP_PROJECT,FSP_LANG_ID:15306,25|archive-url=https://archive.today/20130213052907/http://www.cenelec.eu/dyn/www/f?p=104:110:1546953662480229::::FSP_PROJECT,FSP_LANG_ID:15306,25|archive-date=2013-02-13|title = CENELEC – Standards Development – List of Technical Bodies}}</ref>

<ref name="CENELECxxxx">{{Cite web|url=http://www.cenelec.eu/dyn/www/f?p=104:110:6177007965168887::::FSP_PROJECT,FSP_LANG_ID:20776,25|archive-url=https://archive.today/20120722151947/http://www.cenelec.eu/dyn/www/f?p=104:110:6177007965168887::::FSP_PROJECT,FSP_LANG_ID:20776,25|archive-date=2012-07-22|title = CENELEC – Standards Development – List of Technical Bodies}}</ref>

<ref name="customxxxx">As used in this article, the term '''customary binary prefix''' or similar refers to prefixes such as kilo, mega, giga, etc., borrowed from the similarly named ]es but used to denote a power of 1024.</ref>

<ref name="HP2012">{{cite web|url=http://welcome.hp.com/country/us/en/welcome.html |title=Hewlett-Packard |publisher=Welcome.hp.com |access-date=2012-01-26}}</ref>

<ref name="sony2017">{{cite web|url=http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&categoryId=16155&SR=nav:shop:computers:desktops:ss&ref=http://www.sony.com/index.php|title=Consumer Electronics – Sony US|website=Sonystyle.com|access-date=30 December 2017|archive-date=2011-06-16 |archive-url=https://web.archive.org/web/20110616080047/http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&categoryId=16155&SR=nav%3Ashop%3Acomputers%3Adesktops%3Ass&ref=http%3A%2F%2Fwww.sony.com%2Findex.php}}</ref>

<ref name="forall2012">{{cite web|url=http://www.4allmemory.com/index.cfm?fuseaction=search.rdram_rambus_pc1066 |title=4AllMemory.com |publisher=4AllMemory.com |access-date=2012-01-26}}</ref>

<ref name="linux2001">{{cite web |url=http://www.annodex.net/cgi-bin/man/man2html?units+7 |title=Units |access-date=2007-05-20 |date=2001-12-22 |work=] |quote=When the Linux kernel boots and says <code>hda: 120064896 sectors (61473&nbsp;MB) w/2048KiB Cache</code> the MB are megabytes and the KiB are kibibytes. |url-status=usurped |archive-url=https://web.archive.org/web/20070902124532/http://www.annodex.net/cgi-bin/man/man2html?units+7 |archive-date=2 September 2007 }}</ref>

<ref name="ESR2012">{{cite web|url=https://lwn.net/2002/0103/a/esr-kibi.php3 |title=ESR post on LKML |publisher=Lwn.net |access-date=2012-01-26}}</ref>

<ref name="ubuntu2012">{{cite web|url=http://www.neowin.net/news/ubuntu-implements-units-policy-will-switch-to-base-10-units-in-future-release |title=Ubuntu implements units policy, will switch to base-10 units in future release |publisher=Neowin.net |access-date=2012-01-26}}</ref>

<ref name="ubuntu2012b">{{cite web|url=https://wiki.ubuntu.com/UnitsPolicy |title=UnitsPolicy – Ubuntu Wiki |publisher=Wiki.ubuntu.com |access-date=2012-01-26}}</ref>

<ref name="snow2009">{{cite magazine |url=http://www.macworld.co.uk/mac/news/index.cfm?RSS&NewsID=27034 |title=Snow Leopard's new maths |magazine=Macworld |date=2009-08-28 |access-date=2011-04-13 }}{{Dead link|date=May 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

<ref name="apple2018">{{cite web |url=https://support.apple.com/en-ca/HT201402 |title=How iOS and macOS report storage capacity |publisher=Apple Inc |date=2018-02-27 |access-date=2021-06-27}}</ref>

<ref name="JEDEC-terms">{{cite web | author = JEDEC Solid State Technology Association | title = JEDEC Standard No. 100B.01 – Terms, Definitions, and Letter Symbols for Microcomputers, Microprocessors, and Memory Integrated Circuits | date = December 2002 | page = 8 | url = http://www.jedec.org/download/search/JESD100B01.pdf | access-date = 2010-03-07 | quote = The definitions of kilo, giga, and mega based on powers of two are included only to reflect common usage. IEEE/ASTM SI 10-1997 states "This practice frequently leads to confusion and is deprecated." }} (Requires free registration and login.)</ref>

<ref name="JEDEC-ddr3">{{cite web |title=DDR3 SDRAM Standard |author=JEDEC |date = September 2009|access-date=2010-02-04 |url=http://www.jedec.org/standards-documents/docs/jesd-79-3d }}</ref>

<ref name="JEDEC-ddr2">{{cite web |title=DDR2 SDRAM Standard |author=JEDEC |date = November 2009|access-date=2010-02-04 |url=http://www.jedec.org/standards-documents/docs/jesd-79-2e }}</ref>

<ref name="JEDEC-configs">{{cite web |title=Memory Configurations |author=JEDEC |access-date=2010-02-04 |url=http://www.jedec.org/standards-documents/technology-focus-areas/memory-configurations-jesd21-c }}</ref>

<ref name="JEDEC-configs-toc">{{cite web |title=Memory Configurations Table of Contents |author=JEDEC |access-date=2010-02-04 |url=http://www.jedec.org/sites/default/files/21C_TOCR18.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.jedec.org/sites/default/files/21C_TOCR18.pdf |archive-date=2022-10-09 |url-status=live }}</ref>

<ref name="JEDEC-configs-terms">{{cite web |title=Terms and Definitions |author=JEDEC |access-date=2010-02-04 |url=http://www.jedec.org/sites/default/files/2_00R19.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.jedec.org/sites/default/files/2_00R19.pdf |archive-date=2022-10-09 |url-status=live }}</ref>

<ref name="hita2009">{{dead link|date=October 2015}}{{cbignore}}</ref>

<ref name="sams2011">{{cite web|url=http://www.samsung.com/global/business/hdd/faqView.do?b2b_bbs_msg_id=167 |archive-url=https://web.archive.org/web/20110616021347/http://www.samsung.com/global/business/hdd/faqView.do?b2b_bbs_msg_id=167 |archive-date=2011-06-16 |title=FAQs|website=Samsung.com |access-date=30 December 2017}}</ref>

<ref name="seag2017">{{cite web |url=http://www.seagate.com/docs/pdf/whitepaper/storage_solutions_guide.pdf |title=Storage Solutions Guide |website=Seagate |access-date=2010-03-04 |archive-url=https://web.archive.org/web/20100331115539/http://www.seagate.com/docs/pdf/whitepaper/storage_solutions_guide.pdf |archive-date=2010-03-31 }}</ref>

<ref name="toshi2009">{{cite press release |url=http://sdd.toshiba.com/techdocs/MKxx33GSG_MK1235GSL_r1.pdf |archive-url=https://web.archive.org/web/20091122075109/http://sdd.toshiba.com/techdocs/MKxx33GSG_MK1235GSL_r1.pdf |archive-date=22 November 2009 |title=Toshiba Introduces Two 1.8-inch Hard Disk Drive Families For Both High Performance and Long Battery Life in Mobile Computing Applications |publisher=Toshiba |date=4 November 2009 |access-date=30 December 2017}}</ref>

<ref name="WDC2005">{{cite web |title=WD Model and Order Numbers |url=http://www.wdc.com/en/library/2579-001028.pdf |archive-url=https://web.archive.org/web/20050824091308/http://www.wdc.com/en/library/2579-001028.pdf |archive-date=2005-08-24 }}</ref>

<ref name="sd-cap-disclaimer">{{cite web |url=http://www.sandisk.com/Assets/Categories/Products/card_capacitydisclaimer.pdf |title=Secure Digital Capacity Disclaimer |work=sandisk.com |publisher=] |access-date=2014-06-20 |archive-url=https://web.archive.org/web/20130227015453/http://www.sandisk.com/Assets/Categories/Products/card_capacitydisclaimer.pdf |archive-date=2013-02-27 }}</ref>

<ref name="msoftxxxx">{{cite web |last=Microsoft |title=Determining Actual Disk Size: Why 1.44&nbsp;MB Should Be 1.40&nbsp;MB |work=Article ID: 121839 |publisher=Microsoft |date=2003-05-06 |url=http://support.microsoft.com/kb/121839 |access-date=2007-07-07}} "The 1.44-megabyte (MB) value associated with the 3.5-inch disk format does not represent the actual size or free space of these disks. Although its size has been popularly called 1.44&nbsp;MB, the correct size is actually 1.40&nbsp;MB."</ref>

<ref name="dvdcap"> {{webarchive |url=https://web.archive.org/web/20110102065839/http://www.osta.org/technology/pdf/dvdqa.pdf#page=20 |date=2 January 2011 }}</ref>

<ref name="cdromcap">{{cite web |url=http://www.videohelp.com/forum/userguides/135642.php |title=Data capacity of CDs |publisher=Videohelp.com |access-date=2012-01-26 |archive-date=2006-07-15 |archive-url=https://web.archive.org/web/20060715075021/http://www.videohelp.com/forum/userguides/135642.php |url-status=dead }}</ref>

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<ref name="ECMA2013">{{cite web|url=http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-319.pdf|title=Data Interchange on 12,7 mm 384-Track Magnetic Tape Cartridges – Ultrium-1 Format|website=Ecma-international.org|access-date=30 December 2017|archive-url=https://web.archive.org/web/20130917015428/http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-319.pdf|archive-date=2013-09-17}}</ref>

<ref name="toshi2017">{{cite web|url=http://www.toshiba-tdmt.com.tw/english/products/overview.aspx|title=Client: Client HDD – Toshiba|website=Toshiba-tdmt.com.tw|access-date=30 December 2017|archive-date=2021-04-26 |archive-url=https://web.archive.org/web/20210426174348/http://www.toshiba-tdmt.com.tw/english/products/overview.aspx|url-status=dead}}</ref>

<ref name="IBMaxxxx">{{cite web|url=http://pic.dhe.ibm.com/infocenter/etc/cust/index.jsp?topic=/com.ibm.storage.etc.doc/etc_data_storage_values.html|archive-url=https://archive.today/20140317230133/http://pic.dhe.ibm.com/infocenter/etc/cust/index.jsp?topic=/com.ibm.storage.etc.doc/etc_data_storage_values.html|archive-date=17 March 2014|title=IBM Knowledge Center|website=Pic.dhe.ibm.com|access-date=30 December 2017}}</ref>

<ref name="resp2011">DeRespinis, F., Hayward, P., Jenkins, J., Laird, A., McDonald, L., and Radzinski, E. (2011): ''The IBM style guide: conventions for writers and editors''. IBM Press. quote: "To help avoid inaccuracy (especially with the larger prefixes) and potential ambiguity, the International Electrotechnical Commission (IEC) in 2000 adopted a set of prefixes specifically for binary multipliers (See IEC 60027-2). Their use is now supported by the United States National Institute of Standards and Technology (NIST) and incorporated into ISO 80000. They are also required by EU law and in certain contexts in the US. However, most documentation and products in the industry continue to use SI prefixes when referring to binary multipliers. In product documentation, follow the same standard that is used in the product itself (for example, in the interface or firmware). Whether you choose to use IEC prefixes for powers of 2 and SI prefixes for powers of 10, or use SI prefixes for a dual purpose ... be consistent in your usage and explain to the user your adopted system."</ref>

<ref name="pate2011">{{cite web |title=Patent WO2012098399A2 – Low-power oscillator – Google Patents |website=Google.com |url=https://patents.google.com/patent/WO2012098399A2/en |access-date=2016-06-23}}</ref>

<ref name="ains2022">{{cite journal |title=A terminology standard for underwater acoustics and the benefits of international standardization. |author-last1=Ainslie |author-first1=Michael A. |author-last2=Halvorsen |author-first2=Michele B. |author-last3=Robinson |author-first3=Stephen P. |orig-date=2021-11-09 |date=January 2022 |issn=0364-9059 |eissn=1558-1691 |journal=] |publisher=] |volume=47 |issue=1 |pages=179–200 |doi=10.1109/JOE.2021.3085947 |bibcode=2022IJOE...47..179A |s2cid=243948953 |doi-access=free }} (22 pages)</ref>

}}

== Further reading == == Further reading ==
* {{cite web|url=http://www.iec.ch/zone/si/si_bytes.htm|title=When is a kilobyte a kibibyte? And an MB an MiB?|publisher=International Electrotechnical Commission|date=]}} An introduction to binary prefixes * {{cite web|url=http://www.iec.ch/zone/si/si_bytes.htm|archive-url=https://web.archive.org/web/20090403051731/http://www.iec.ch/zone/si/si_bytes.htm|archive-date=2009-04-03|title=When is a kilobyte a kibibyte? And an MB an MiB?|publisher=International Electrotechnical Commission|date=2007-02-12}} An introduction to binary prefixes
* {{cite web|url=http://physics.nist.gov/cuu/Units/binary.html|title=Prefixes for binary multiples|publisher=]}} * {{cite web|url=http://physics.nist.gov/cuu/Units/binary.html|title=Prefixes for binary multiples|publisher=]}}
* {{cite press release|url=http://www.nist.gov/public_affairs/techbeat/tb9903.htm#Information%20Technology|title=Get Ready for the mebi, gibi and tebi|publisher=]|date=]}} * {{Cite press release|url=https://www.nist.gov/public_affairs/techbeat/tb9903.htm#Information%20Technology|title=Get Ready for the mebi, gibi and tebi|publisher=]|date=1999-03-02|access-date=2017-07-13 |archive-date=2016-08-20 |archive-url=https://web.archive.org/web/20160820141603/http://www.nist.gov/public_affairs/techbeat/tb9903.htm#Information%20Technology}}
* {{cite web|url=http://www.cl.cam.ac.uk/~mgk25/information-units.txt|title=What is a Megabyte ...?|author=Markus Kuhn|date=]}} &mdash; a 1996&ndash;1999 paper on bits, bytes, prefixes and symbols * {{cite web|url=http://www.cl.cam.ac.uk/~mgk25/information-units.txt|title=What is a Megabyte ...?|author-first=Markus |author-last=Kuhn|author-link=Markus Kuhn (computer scientist)|date=1996-12-29}}—a 1996–1999 paper on bits, bytes, prefixes and symbols
* {{cite web|url=http://homepages.tesco.net/~J.deBoynePollard/FGA/1mb44-is-not-a-standard-floppy-disc-size.html|author=Jonathan de Boyne Pollard|title=There is no such thing as a 1.44 MB standard format floppy disc}} * {{cite web|url=http://jdebp.eu./FGA/1mb44-is-not-a-standard-floppy-disc-size.html|author-first=Jonathan|author-last=de Boyne Pollard|title=There is no such thing as a 1.44&nbsp;MB standard format floppy disc|work=Frequently Given Answers|archive-url=https://web.archive.org/web/20161007222128/https://jdebp.eu/FGA/1mb44-is-not-a-standard-floppy-disc-size.html|archive-date=2016-10-07}}
* {{cite web|url=http://www.quinion.com/words/turnsofphrase/tp-kib1.htm|title=Kibibyte|date=]|author=Michael Quinion|work=World Wide Words}} &mdash; Another description of binary prefixes * {{cite web|url=http://www.quinion.com/words/turnsofphrase/tp-kib1.htm|title=Kibibyte|date=1999-08-21|author=Michael Quinion|work=World Wide Words|access-date=2002-11-13 |archive-date=2004-06-12 |archive-url=https://web.archive.org/web/20040612044148/http://www.quinion.com/words/turnsofphrase/tp-kib1.htm}}—Another description of binary prefixes
* {{cite paper|format=PDF|url=http://www.wiebetech.com/pressreleases/BillionEqualBillion.pdf|title=When One Billion does not equal One Billion, or: Why your computer's disk drive capacity doesn’t appear to match the stated capacity|author=James Wiebe|date=]}} &mdash; White-paper on the controversy over drive capacities * {{Cite press release |url=http://www.wiebetech.com/pressreleases/BillionEqualBillion.pdf|title=When One Billion does not equal One Billion, or: Why your computer's disk drive capacity doesn't appear to match the stated capacity |website=WiebeTech |author=James Wiebe|date=2003-10-09|access-date=2010-01-22|journal=|archive-date=2013-12-04 |archive-url=https://web.archive.org/web/20131204100206/http://www.wiebetech.com/pressreleases/BillionEqualBillion.pdf}}—White-paper on the controversy over drive capacities

== External links == == External links ==
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* ; {{Webarchive|url=https://web.archive.org/web/20150102192754/http://knowledge.seagate.com/articles/en_US/FAQ/002046en?language=en_US |date=2015-01-02 }}
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Latest revision as of 21:39, 6 January 2025

Symbol placed before units of digital information to indicate multiplication by a power of two This article is about powers-of-two prefixes for measurement units like bit and byte. For notations for the radix of a numeral, see Integer literal § Affixes.

"Gibi" redirects here. For other uses, see Gibi (disambiguation).
Prefixes for decimal and binary multiples
Decimal
Value SI
1000 10 k kilo
1000 10 M mega
1000 10 G giga
1000 10 T tera
1000 10 P peta
1000 10 E exa
1000 10 Z zetta
1000 10 Y yotta
1000 10 R ronna
1000 10 Q quetta
Binary
Value IEC JEDEC
1024 2 Ki kibi K kilo
1024 2 Mi mebi M mega
1024 2 Gi gibi G giga
1024 2 Ti tebi T tera
1024 2 Pi pebi
1024 2 Ei exbi
1024 2 Zi zebi
1024 2 Yi yobi

A binary prefix is a unit prefix that indicates a multiple of a unit of measurement by an integer power of two. The most commonly used binary prefixes are kibi (symbol Ki, meaning 2 = 1024), mebi (Mi, 2 = 1048576), and gibi (Gi, 2 = 1073741824). They are most often used in information technology as multipliers of bit and byte, when expressing the capacity of storage devices or the size of computer files.

The binary prefixes "kibi", "mebi", etc. were defined in 1999 by the International Electrotechnical Commission (IEC), in the IEC 60027-2 standard (Amendment 2). They were meant to replace the metric (SI) decimal power prefixes, such as "kilo" (k, 10 = 1000), "mega" (M, 10 = 1000000) and "giga" (G, 10 = 1000000000), that were commonly used in the computer industry to indicate the nearest powers of two. For example, a memory module whose capacity was specified by the manufacturer as "2 megabytes" or "2 MB" would hold 2 × 2 = 2097152 bytes, instead of 2 × 10 = 2000000.

On the other hand, a hard disk whose capacity is specified by the manufacturer as "10 gigabytes" or "10 GB", holds 10 × 10 = 10000000000 bytes, or a little more than that, but less than 10 × 2 = 10737418240 and a file whose size is listed as "2.3 GB" may have a size closer to 2.3 × 2 ≈ 2470000000 or to 2.3 × 10 = 2300000000, depending on the program or operating system providing that measurement. This kind of ambiguity is often confusing to computer system users and has resulted in lawsuits. The IEC 60027-2 binary prefixes have been incorporated in the ISO/IEC 80000 standard and are supported by other standards bodies, including the BIPM, which defines the SI system, the US NIST, and the European Union.

Prior to the 1999 IEC standard, some industry organizations, such as the Joint Electron Device Engineering Council (JEDEC), attempted to redefine the terms kilobyte, megabyte, and gigabyte, and the corresponding symbols KB, MB, and GB in the binary sense, for use in storage capacity measurements. However, other computer industry sectors (such as magnetic storage) continued using those same terms and symbols with the decimal meaning. Since then, the major standards organizations have expressly disapproved the use of SI prefixes to denote binary multiples, and recommended or mandated the use of the IEC prefixes for that purpose, but the use of SI prefixes in this sense has persisted in some fields.

Definitions

Specific units of IEC 60027-2 A.2 and ISO/IEC 80000:13-2008
IEC prefix Representations
Name Symbol Base 2 Base 1024 Value Base 10
kibi Ki 2 1024 1024 = 1.024×10
mebi Mi 2 1024 1048576 ≈ 1.049×10
gibi Gi 2 1024 1073741824 ≈ 1.074×10
tebi Ti 2 1024 1099511627776 ≈ 1.100×10
pebi Pi 2 1024 1125899906842624 ≈ 1.126×10
exbi Ei 2 1024 1152921504606846976 ≈ 1.153×10
zebi Zi 2 1024 1180591620717411303424 ≈ 1.181×10
yobi Yi 2 1024 1208925819614629174706176 ≈ 1.209×10

In 2022, the International Bureau of Weights and Measures (BIPM) adopted the decimal prefixes ronna for 1000 and quetta for 1000. In analogy to the existing binary prefixes, a consultation paper of the International Committee for Weights and Measures' Consultative Committee for Units (CCU) suggested the prefixes robi (Ri, 1024) and quebi (Qi, 1024) for their binary counterparts, but as of 2022, no corresponding binary prefixes have been adopted.

Comparison of binary and decimal prefixes

The relative difference between the values in the binary and decimal interpretations increases, when using the SI prefixes as the base, from 2.4% for kilo to nearly 27% for the quetta prefix. Although the prefixes ronna and quetta have been defined, as of 2022 no names have been officially assigned to the corresponding binary prefixes.

Prefix Binary ÷ Decimal Decimal ÷ Binary
kilo kibi 1.024 (+2.4%)   0.9766 (−2.3%)  
mega mebi 1.049 (+4.9%)   0.9537 (−4.6%)  
giga gibi 1.074 (+7.4%)   0.9313 (−6.9%)  
tera tebi 1.100 (+10.0%)   0.9095 (−9.1%)  
peta pebi 1.126 (+12.6%)   0.8882 (−11.2%)  
exa exbi 1.153 (+15.3%)   0.8674 (−13.3%)  
zetta zebi 1.181 (+18.1%)   0.8470 (−15.3%)  
yotta yobi 1.209 (+20.9%)   0.8272 (−17.3%)  
ronna 1.238 (+23.8%)   0.8078 (−19.2%)  
quetta 1.268 (+26.8%)   0.7889 (−21.1%)  

History

See also: Timeline of binary prefixes

Early prefixes

The original metric system adopted by France in 1795 included two binary prefixes named double- (2×) and demi- (⁠1/2⁠×). However, these were not retained when the SI prefixes were internationally adopted by the 11th CGPM conference in 1960.

Storage capacity

Main memory

Early computers used one of two addressing methods to access the system memory; binary (base 2) or decimal (base 10). For example, the IBM 701 (1952) used a binary methods and could address 2048 words of 36 bits each, while the IBM 702 (1953) used a decimal system, and could address ten thousand 7-bit words.

By the mid-1960s, binary addressing had become the standard architecture in most computer designs, and main memory sizes were most commonly powers of two. This is the most natural configuration for memory, as all combinations of states of their address lines map to a valid address, allowing easy aggregation into a larger block of memory with contiguous addresses.

While early documentation specified those memory sizes as exact numbers such as 4096, 8192, or 16384 units (usually words, bytes, or bits), computer professionals also started using the long-established metric system prefixes "kilo", "mega", "giga", etc., defined to be powers of 10, to mean instead the nearest powers of two; namely, 2 = 1024, 2 = 1024, 2 = 1024, etc. The corresponding metric prefix symbols ("k", "M", "G", etc.) were used with the same binary meanings. The symbol for 2 = 1024 could be written either in lower case ("k") or in uppercase ("K"). The latter was often used intentionally to indicate the binary rather than decimal meaning. This convention, which could not be extended to higher powers, was widely used in the documentation of the IBM 360 (1964) and of the IBM System/370 (1972), of the CDC 7600, of the DEC PDP-11/70 (1975) and of the DEC VAX-11/780 (1977).

In other documents, however, the metric prefixes and their symbols were used to denote powers of 10, but usually with the understanding that the values given were approximate, often truncated down. Thus, for example, a 1967 document by Control Data Corporation (CDC) abbreviated "2 = 64 × 1024 = 65536 words" as "65K words" (rather than "64K" or "66K"), while the documentation of the HP 21MX real-time computer (1974) denoted 3 × 2 = 192 × 1024 = 196608 as "196K" and 2 = 1048576 as "1M".

These three possible meanings of "k" and "K" ("1024", "1000", or "approximately 1000") were used loosely around the same time, sometimes by the same company. The HP 3000 business computer (1973) could have "64K", "96K", or "128K" bytes of memory. The use of SI prefixes, and the use of "K" instead of "k" remained popular in computer-related publications well into the 21st century, although the ambiguity persisted. The correct meaning was often clear from the context; for instance, in a binary-addressed computer, the true memory size had to be either a power of 2, or a small integer multiple thereof. Thus a "512 megabyte" RAM module was generally understood to have 512 × 1024 = 536870912 bytes, rather than 512000000.

Hard disks

In specifying disk drive capacities, manufacturers have always used conventional decimal SI prefixes representing powers of 10. Storage in a rotating disk drive is organized in platters and tracks whose sizes and counts are determined by mechanical engineering constraints so that the capacity of a disk drive has hardly ever been a simple multiple of a power of 2. For example, the first commercially sold disk drive, the IBM 350 (1956), had 50 physical disk platters containing a total of 50000 sectors of 100 characters each, for a total quoted capacity of 5 million characters.

Moreover, since the 1960s, many disk drives used IBM's disk format, where each track was divided into blocks of user-specified size; and the block sizes were recorded on the disk, subtracting from the usable capacity. For example, the IBM 3336 disk pack was quoted to have a 200-megabyte capacity, achieved only with a single 13030-byte block in each of its 808 × 19 tracks.

Decimal megabytes were used for disk capacity by the CDC in 1974. The Seagate ST-412, one of several types installed in the IBM PC/XT, had a capacity of 10027008 bytes when formatted as 306 × 4 tracks and 32 256-byte sectors per track, which was quoted as "10 MB". Similarly, a "300 GB" hard drive can be expected to offer only slightly more than 300×10 = 300000000000, bytes, not 300 × 2 (which would be about 322×10 bytes or "322 GB"). The first terabyte (SI prefix, 1000000000000 bytes) hard disk drive was introduced in 2007. Decimal prefixes were generally used by information processing publications when comparing hard disk capacities.

Some programs and operating systems, such as Microsoft Windows, still use "MB" and "GB" to denote binary prefixes even when displaying disk drive capacities and file sizes, as did Classic Mac OS. Thus, for example, the capacity of a "10 MB" (decimal "M") disk drive could be reported as "9.56 MB", and that of a "300 GB" drive as "279.4 GB". Some operating systems, such as Mac OS X, Ubuntu, and Debian, have been updated to use "MB" and "GB" to denote decimal prefixes when displaying disk drive capacities and file sizes. Some manufacturers, such as Seagate Technology, have released recommendations stating that properly-written software and documentation should specify clearly whether prefixes such as "K", "M", or "G" mean binary or decimal multipliers.

Floppy disks

Floppy disks used a variety of formats, and their capacities was usually specified with SI-like prefixes "K" and "M" with either decimal or binary meaning. The capacity of the disks was often specified without accounting for the internal formatting overhead, leading to more irregularities.

The early 8-inch diskette formats could contain less than a megabyte with the capacities of those devices specified in kilobytes, kilobits or megabits.

The 5.25-inch diskette sold with the IBM PC AT could hold 1200 × 1024 = 1228800 bytes, and thus was marketed as "1200 KB" with the binary sense of "KB". However, the capacity was also quoted "1.2 MB", which was a hybrid decimal and binary notation, since the "M" meant 1000 × 1024. The precise value was 1.2288 MB (decimal) or 1.171875 MiB (binary).

The 5.25-inch Apple Disk II had 256 bytes per sector, 13 sectors per track, 35 tracks per side, or a total capacity of 116480 bytes. It was later upgraded to 16 sectors per track, giving a total of 140 × 2 = 143360 bytes, which was described as "140KB" using the binary sense of "K".

The most recent version of the physical hardware, the "3.5-inch diskette" cartridge, had 720 512-byte blocks (single-sided). Since two blocks comprised 1024 bytes, the capacity was quoted "360 KB", with the binary sense of "K". On the other hand, the quoted capacity of "1.44 MB" of the High Density ("HD") version was again a hybrid decimal and binary notation, since it meant 1440 pairs of 512-byte sectors, or 1440 × 2 = 1474560 bytes. Some operating systems displayed the capacity of those disks using the binary sense of "MB", as "1.4 MB" (which would be 1.4 × 2 ≈ 1468000 bytes). User complaints forced both Apple and Microsoft to issue support bulletins explaining the discrepancy.

Optical disks

When specifying the capacities of optical compact discs, "megabyte" and "MB" usually meant 1024 bytes. Thus a "700-MB" (or "80-minute") CD has a nominal capacity of about 700 MiB, which is approximately 730 MB (decimal).

On the other hand, capacities of other optical disc storage media like DVD, Blu-ray Disc, HD DVD and magneto-optical (MO) have been generally specified in decimal gigabytes ("GB"), that is, 1000 bytes. In particular, a typical "4.7 GB" DVD has a nominal capacity of about 4.7×10 bytes, which is about 4.38 GiB.

Tape drives and media

Tape drive and media manufacturers have generally used SI decimal prefixes to specify the maximum capacity, although the actual capacity would depend on the block size used when recording.

Data and clock rates

Computer clock frequencies are always quoted using SI prefixes in their decimal sense. For example, the internal clock frequency of the original IBM PC was 4.77 MHz, that is 4770000 Hz.

Similarly, digital information transfer rates are quoted using decimal prefixe. The Parallel ATA "100 MB/s" disk interface can transfer 100000000 bytes per second, and a "56 Kb/s" modem transmits 56000 bits per second. Seagate specified the sustained transfer rate of some hard disk drive models with both decimal and IEC binary prefixes. The standard sampling rate of music compact disks, quoted as 44.1 kHz, is indeed 44100 samples per second. A "1 Gb/s" Ethernet interface can receive or transmit up to 10 bits per second, or 125000000 bytes per second within each packet. A "56k" modem can encode or decode up to 56000 bits per second.

Decimal SI prefixes are also generally used for processor-memory data transfer speeds. A PCI-X bus with 66 MHz clock and 64 bits wide can transfer 66000000 64-bit words per second, or 4224000000 bit/s = 528000000 B/s, which is usually quoted as 528 MB/s. A PC3200 memory on a double data rate bus, transferring 8 bytes per cycle with a clock speed of 200 MHz has a bandwidth of 200000000 × 8 × 2 = 3200000000 B/s, which would be quoted as 3.2 GB/s.

Ambiguous standards

The ambiguous usage of the prefixes "kilo ("K" or "k"), "mega" ("M"), and "giga" ("G"), as meaning both powers of 1000 or (in computer contexts) of 1024, has been recorded in popular dictionaries, and even in some obsolete standards, such as ANSI/IEEE 1084-1986 and ANSI/IEEE 1212-1991, IEEE 610.10-1994, and IEEE 100-2000. Some of these standards specifically limited the binary meaning to multiples of "byte" ("B") or "bit" ("b").

Early binary prefix proposals

Before the IEC standard, several alternative proposals existed for unique binary prefixes, starting in the late 1960s. In 1996, Markus Kuhn proposed the extra prefix "di" and the symbol suffix or subscript "2" to mean "binary"; so that, for example, "one dikilobyte" would mean "1024 bytes", denoted "K2B" or "K2B".

In 1968, Donald Morrison proposed to use the Greek letter kappa (κ) to denote 1024, κ to denote 1024, and so on. (At the time, memory size was small, and only K was in widespread use.) In the same year, Wallace Givens responded with a suggestion to use bK as an abbreviation for 1024 and bK2 or bK for 1024, though he noted that neither the Greek letter nor lowercase letter b would be easy to reproduce on computer printers of the day. Bruce Alan Martin of Brookhaven National Laboratory proposed that, instead of prefixes, binary powers of two were indicated by the letter B followed by the exponent, similar to E in decimal scientific notation. Thus one would write 3B20 for 3 × 2. This convention is still used on some calculators to present binary floating point-numbers today.

In 1969, Donald Knuth, who uses decimal notation like 1 MB = 1000 kB, proposed that the powers of 1024 be designated as "large kilobytes" and "large megabytes", with abbreviations KKB and MMB.

Consumer confusion

The ambiguous meanings of "kilo", "mega", "giga", etc., has caused significant consumer confusion, especially in the personal computer era. A common source of confusion was the discrepancy between the capacities of hard drives specified by manufacturers, using those prefixes in the decimal sense, and the numbers reported by operating systems and other software, that used them in the binary sense, such as the Apple Macintosh in 1984. For example, a hard drive marketed as "1 TB" could be reported as having only "931 GB". The confusion was compounded by fact that RAM manufacturers used the binary sense too.

Legal disputes

The different interpretations of disk size prefixes led to class action lawsuits against digital storage manufacturers. These cases involved both flash memory and hard disk drives.

Early cases

Early cases (2004–2007) were settled prior to any court ruling with the manufacturers admitting no wrongdoing but agreeing to clarify the storage capacity of their products on the consumer packaging. Accordingly, many flash memory and hard disk manufacturers have disclosures on their packaging and web sites clarifying the formatted capacity of the devices or defining MB as 1 million bytes and 1 GB as 1 billion bytes.

Willem Vroegh v. Eastman Kodak Company

On 20 February 2004, Willem Vroegh filed a lawsuit against Lexar Media, Dane–Elec Memory, Fuji Photo Film USA, Eastman Kodak Company, Kingston Technology Company, Inc., Memorex Products, Inc.; PNY Technologies Inc., SanDisk Corporation, Verbatim Corporation, and Viking Interworks alleging that their descriptions of the capacity of their flash memory cards were false and misleading.

Vroegh claimed that a 256 MB Flash Memory Device had only 244 MB of accessible memory. "Plaintiffs allege that Defendants marketed the memory capacity of their products by assuming that one megabyte equals one million bytes and one gigabyte equals one billion bytes." The plaintiffs wanted the defendants to use the customary values of 1024 for megabyte and 1024 for gigabyte. The plaintiffs acknowledged that the IEC and IEEE standards define a MB as one million bytes but stated that the industry has largely ignored the IEC standards.

The parties agreed that manufacturers could continue to use the decimal definition so long as the definition was added to the packaging and web sites. The consumers could apply for "a discount of ten percent off a future online purchase from Defendants' Online Stores Flash Memory Device".

Orin Safier v. Western Digital Corporation

On 7 July 2005, an action entitled Orin Safier v. Western Digital Corporation, et al. was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-05-442812. The case was subsequently moved to the Northern District of California, Case No. 05-03353 BZ.

Although Western Digital maintained that their usage of units is consistent with "the indisputably correct industry standard for measuring and describing storage capacity", and that they "cannot be expected to reform the software industry", they agreed to settle in March 2006 with 14 June 2006 as the Final Approval hearing date.

Western Digital offered to compensate customers with a gratis download of backup and recovery software that they valued at US$30. They also paid $500000 in fees and expenses to San Francisco lawyers Adam Gutride and Seth Safier, who filed the suit. The settlement called for Western Digital to add a disclaimer to their later packaging and advertising. Western Digital had this footnote in their settlement. "Apparently, Plaintiff believes that he could sue an egg company for fraud for labeling a carton of 12 eggs a 'dozen', because some bakers would view a 'dozen' as including 13 items."

Cho v. Seagate Technology (US) Holdings, Inc.

A lawsuit (Cho v. Seagate Technology (US) Holdings, Inc., San Francisco Superior Court, Case No. CGC-06-453195) was filed against Seagate Technology, alleging that Seagate overrepresented the amount of usable storage by 7% on hard drives sold between 22 March 2001 and 26 September 2007. The case was settled without Seagate admitting wrongdoing, but agreeing to supply those purchasers with gratis backup software or a 5% refund on the cost of the drives.

Dinan et al. v. SanDisk LLC

On 22 January 2020, the district court of the Northern District of California ruled in favor of the defendant, SanDisk, upholding its use of "GB" to mean 1000000000 bytes.

IEC 1999 Standard

In 1995, the International Union of Pure and Applied Chemistry's (IUPAC) Interdivisional Committee on Nomenclature and Symbols (IDCNS) proposed the prefixes "kibi" (short for "kilobinary"), "mebi" ("megabinary"), "gibi" ("gigabinary") and "tebi" ("terabinary"), with respective symbols "kb", "Mb", "Gb" and "Tb", for binary multipliers. The proposal suggested that the SI prefixes should be used only for powers of 10; so that a disk drive capacity of "500 gigabytes", "0.5 terabytes", "500 GB", or "0.5 TB" should all mean 500×10 bytes, exactly or approximately, rather than 500 × 2 (= 536870912000) or 0.5 × 2 (= 549755813888).

The proposal was not accepted by IUPAC at the time, but was taken up in 1996 by the Institute of Electrical and Electronics Engineers (IEEE) in collaboration with the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC). The prefixes "kibi", "mebi", "gibi" and "tebi" were retained, but with the symbols "Ki" (with capital "K"), "Mi", "Gi" and "Ti" respectively.

In January 1999, the IEC published this proposal, with additional prefixes "pebi" ("Pi") and "exbi" ("Ei"), as an international standard (IEC 60027-2 Amendment 2) The standard reaffirmed the BIPM's position that the SI prefixes should always denote powers of 10. The third edition of the standard, published in 2005, added prefixes "zebi" and "yobi", thus matching all then-defined SI prefixes with binary counterparts.

The harmonized ISO/IEC IEC 80000-13:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 (those defining prefixes for binary multiples). The only significant change is the addition of explicit definitions for some quantities. In 2009, the prefixes kibi-, mebi-, etc. were defined by ISO 80000-1 in their own right, independently of the kibibyte, mebibyte, and so on.

The BIPM standard JCGM 200:2012 "International vocabulary of metrology – Basic and general concepts and associated terms (VIM), 3rd edition" lists the IEC binary prefixes and states "SI prefixes refer strictly to powers of 10, and should not be used for powers of 2. For example, 1 kilobit should not be used to represent 1024 bits (2 bits), which is 1 kibibit."

The IEC 60027-2 standard recommended operating systems and other software were updated to use binary or decimal prefixes consistently, but incorrect usage of SI prefixes for binary multiples is still common. At the time, the IEEE decided that their standards would use the prefixes "kilo", etc. with their metric definitions, but allowed the binary definitions to be used in an interim period as long as such usage was explicitly pointed out on a case-by-case basis.

Other standards bodies and organizations

The IEC standard binary prefixes are supported by other standardization bodies and technical organizations.

The United States National Institute of Standards and Technology (NIST) supports the ISO/IEC standards for "Prefixes for binary multiples" and has a web page documenting them, describing and justifying their use. NIST suggests that in English, the first syllable of the name of the binary-multiple prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix, and that the second syllable should be pronounced as bee. NIST has stated the SI prefixes "refer strictly to powers of 10" and that the binary definitions "should not be used" for them.

As of 2014, the microelectronics industry standards body JEDEC describes the IEC prefixes in its online dictionary, but acknowledges that the SI prefixes and the symbols "K", "M" and "G" are still commonly used with the binary sense for memory sizes.

On 19 March 2005, the IEEE standard IEEE 1541-2002 ("Prefixes for Binary Multiples") was elevated to a full-use standard by the IEEE Standards Association after a two-year trial period. as of April 2008, the IEEE Publications division does not require the use of IEC prefixes in its major magazines such as Spectrum or Computer.

The International Bureau of Weights and Measures (BIPM), which maintains the International System of Units (SI), expressly prohibits the use of SI prefixes to denote binary multiples, and recommends the use of the IEC prefixes as an alternative since units of information are not included in the SI.

The Society of Automotive Engineers (SAE) prohibits the use of SI prefixes with anything but a power-of-1000 meaning, but does not cite the IEC binary prefixes.

The European Committee for Electrotechnical Standardization (CENELEC) adopted the IEC-recommended binary prefixes via the harmonization document HD 60027-2:2003-03. The European Union (EU) has required the use of the IEC binary prefixes since 2007.

Current practice

The 536870912-byte capacity of these RAM modules is stated as "512 MB" on the label.
GNOME's partition editor uses IEC prefixes to display partition sizes. The total capacity of the 120 × 10-byte disk is displayed as "111.79 GiB".
GNOME's system monitor uses IEC prefixes to show memory size and networking data rate.

Some computer industry participants, such as Hewlett-Packard (HP), and IBM have adopted or recommended IEC binary prefixes as part of their general documentation policies.

As of 2023, the use of SI prefixes with the binary meanings is still prevalent for specifying the capacity of the main memory of computers, of RAM, ROM, EPROM, and EEPROM chips and memory modules, and of the cache of computer processors. For example, a "512-megabyte" or "512 MB" memory module holds 512 MiB; that is, 512 × 2 bytes, not 512 × 10 bytes.

JEDEC continues to include the customary binary definitions of "kilo", "mega", and "giga" in the document Terms, Definitions, and Letter Symbols, and, as of 2010, still used those definitions in their memory standards.

On the other hand, the SI prefixes with powers of ten meanings are generally used for the capacity of external storage units, such as disk drives, solid state drives, and USB flash drives, except for some flash memory chips intended to be used as EEPROMs. However, some disk manufacturers have used the IEC prefixes to avoid confusion. The decimal meaning of SI prefixes is usually also intended in measurements of data transfer rates, and clock speeds.

Some operating systems and other software use either the IEC binary multiplier symbols ("Ki", "Mi", etc.) or the SI multiplier symbols ("k", "M", "G", etc.) with decimal meaning. Some programs, such as the GNU ls command, let the user choose between binary or decimal multipliers. However, some continue to use the SI symbols with the binary meanings, even when reporting disk or file sizes. Some programs may also use "K" instead of "k", with either meaning.

Other uses

While the binary prefixes are almost always used with the units of information, bits and bytes, they may be used with any other unit of measure, when convenient. For example, in signal processing one may need binary multiples of the frequency unit hertz (Hz), for example the kibihertz (KiHz), equal to 1024 Hz.

See also

References

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Platform-dependent units
Metric bit units
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