Gigabyte#Base 10 (decimal)

The term gigabyte has a standard definition of 1000³ bytes, as well as a discouraged{{cite web |url=https://www.courthousenews.com/wp-content/uploads/2020/01/flashdrives.pdf |title=Order Granting Motion to Dismiss |publisher=United States District Court |access-date = 2020-01-24}} meaning of 1024³ bytes. The latter binary usage originated as compromise technical jargon for byte multiples that needed to be expressed in a power of 2, but lacked a convenient name. As 1024 (2¹⁰) is approximately 1000 (10³), roughly corresponding to SI multiples, it was used for binary multiples as well.

In 1998 the International Electrotechnical Commission (IEC) published standards for binary prefixes, requiring that the gigabyte strictly denote 1000³ bytes and gibibyte denote 1024³ bytes. By the end of 2007, the IEC Standard had been adopted by the IEEE, EU, and NIST, and in 2009 it was incorporated in the International System of Quantities. Nevertheless, the term gigabyte continues to be widely used with the following two different meanings:

• 1 GB = {{gaps|1|000|000|000}} bytes (= 1000³ B = 10⁹ B)

Based on powers of 10, this definition uses the prefix giga- as defined in the International System of Units (SI). This is the recommended definition by the International Electrotechnical Commission (IEC).http://physics.nist.gov/cuu/Units/binary.html Prefixes for binary multiples This definition is used in networking contexts and most storage media, particularly hard drives, flash-based storage,[http://apac.sandisk.com/Products/Catalog(1349)-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx SanDisk USB Flash Drive] {{Webarchive|url=https://web.archive.org/web/20080513155718/http://apac.sandisk.com/Products/Catalog%281349%29-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx |date=13 May 2008 }} "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."[http://www.kingston.com/en/usb/storage_chart Storage Chart] "Megabyte (MB) = 1,000,000 bytes; 1 Gigabyte (GB) = 1,000,000,000 bytes; 1TB = 1,000,000,000,000 bytes" and DVDs, and is also consistent with the other uses of the SI prefix in computing, such as CPU clock speeds or measures of performance. The file manager of Mac OS X version 10.6 and later versions are a notable example of this usage in software, which report files sizes in decimal units.{{cite web|url=http://support.apple.com/kb/TS2419 |title=How Mac OS X reports drive capacity |publisher=Apple Inc |date=2009-08-27 |access-date=2009-10-16}}

• 1 GiB = {{gaps|1|073|741|824}} bytes (= 1024³ B = 2³⁰ B).

The binary definition uses powers of the base 2, as does the architectural principle of binary computers.

This usage is widely promulgated by some operating systems, such as Microsoft Windows in reference to computer memory (e.g., RAM). This definition is synonymous with the unambiguous unit gibibyte.

Since the first disk drive, the IBM 350, disk drive manufacturers expressed hard drive capacities using decimal prefixes. With the advent of gigabyte-range drive capacities, manufacturers labelled many consumer hard drive, solid-state drive and USB flash drive capacities in certain size classes expressed in decimal gigabytes, such as "500 GB". The exact capacity of a given drive model is usually slightly larger than the class designation. Practically all manufacturers of hard disk drives and flash-memory disk devices continue to define one gigabyte as {{gaps|1|000|000|000|bytes}}, which is displayed on the packaging. Some operating systems such as Mac OS X,{{Cite web|url=https://support.apple.com/en-us/HT201402|title=How OS X and iOS report storage capacity - Apple Support|website=support.apple.com|access-date=2016-06-29}} iOS, Android,{{Citation needed|date=March 2025}} Ubuntu,{{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 }} and Debian{{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 }} express hard drive capacity or file size using decimal multipliers, while others such as Microsoft Windows (including Windows Phone) report file size using binary multipliers. This discrepancy causes confusion, as a disk with an advertised capacity of, for example, {{nowrap|400 GB}} (meaning {{gaps|400|000|000|000|bytes}}, equal to 372 GiB) might be reported by the operating system as "{{nowrap|372 GB}}".

For RAM, the JEDEC memory standards use IEEE 100 nomenclature which quote the gigabyte as {{gaps|1|073|741|824|bytes}} (2³⁰ bytes).{{Cite journal

| 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

| url = http://www.jedec.org/download/search/JESD100B01.pdf

}}

The difference between units based on decimal and binary prefixes increases as a semi-logarithmic (linear-log) function—for example, the decimal kilobyte value is nearly 98% of the kibibyte, a megabyte is under 96% of a mebibyte, and a gigabyte is just over 93% of a gibibyte value. This means that a 300 GB (279 GiB) hard disk might be indicated variously as "300 GB", "279 GB" or "279 GiB", depending on the operating system. As storage sizes increase and larger units are used, these differences become more pronounced.

A lawsuit decided in 2019 that arose from alleged breach of contract and other claims over the binary and decimal definitions used for "gigabyte" have ended in favour of the manufacturers, with courts holding that the legal definition of gigabyte or GB is 1 GB = 1,000,000,000 (10⁹) bytes (the decimal definition). Specifically, the courts held that "the U.S. Congress has deemed the decimal definition of gigabyte to be the 'preferred' one for the purposes of 'U.S. trade and commerce' .... The California Legislature has likewise adopted the decimal system for all 'transactions in this state'."

Earlier lawsuits had ended in settlement with no court ruling on the question, such as a lawsuit against drive manufacturer Western Digital.{{cite web

| last = Mook

| first = Nate

| date = 2006-06-28

| url = http://www.betanews.com/article/Western-Digital-Settles-Capacity-Suit/1151510648

| title = Western Digital Settles Capacity Suit

| publisher = betanews

| access-date = 2009-03-30

}}{{cite web

| last = Baskin

| first = Scott D.

| date = 2006-02-01

| 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 = Western Digital Corporation

| access-date = 2009-03-30

}} Western Digital settled the challenge and added explicit disclaimers to products that the usable capacity may differ from the advertised capacity.

Seagate was sued on similar grounds and also settled.{{cite news

| last = Judge

| first = Peter

| date = 2007-10-26

| url = https://www.zdnet.com/article/seagate-pays-out-over-gigabyte-definition/

| title = Seagate pays out over gigabyte definition

| work = ZDNet

| access-date = 2014-09-16

}}

Because of their physical design, the capacity of modern computer random-access memory devices, such as DIMM modules, is always a multiple of a power of 1024. It is thus convenient to use prefixes denoting powers of 1024, known as binary prefixes, in describing them. For example, a memory capacity of {{gaps|1|073|741|824|bytes}} (1024³ B) is conveniently expressed as 1 GiB rather than as 1.074 GB. The former specification is, however, often quoted as "1 GB" when applied to random-access memory.{{cite web|last1=Percival|first1=Colin|title=Why is 1 GB equal to 10^9 bytes instead of 2^30?|url=http://www.tarsnap.com/GB-why.html|publisher=tarsnap.com|access-date=1 November 2015}}

Software allocates memory in varying degrees of granularity as needed to fulfill data structure requirements and binary multiples are usually not required. Other computer capacities and rates, like storage hardware size, data transfer rates, clock speeds, operations per second, etc. are usually presented in decimal units. For example, the manufacturer of a "300 GB" hard drive is claiming a capacity of {{gaps|300|000|000|000|bytes}}, not 300 × 1024³ (which would be {{gaps|322|122|547|200}}) bytes.

• One hour of SDTV video at 2.2 Mbit/s is approximately 1 GB.
• Seven minutes of HDTV video at 19.39 Mbit/s is approximately 1 GB.
• 114 minutes of uncompressed CD-quality audio at 1.4 Mbit/s is approximately 1 GB.
• A single-layer DVD+R disc can hold about 4.7 GB.
• A dual-layered DVD+R disc can hold about 8.5 GB.
• A single-layer Blu-ray can hold about 25 GB.
• The largest Nintendo Switch cartridge available on the market holds about 32 GB.
• A dual-layered Blu-ray can hold about 50 GB.
• A triple-layered Ultra HD Blu-ray can hold about 100 GB.

The "gigabyte" symbol is encoded by Unicode at code point {{unichar|3387|Square GB}}.{{cite web |url=https://www.unicode.org/charts/PDF/U3300.pdf |archive-url=https://web.archive.org/web/20010603001437/http://www.unicode.org/charts/PDF/U3300.pdf |archive-date=2001-06-03 |url-status=live |access-date=24 May 2019 |title=The Unicode Standard 12.0 – CJK Compatibility ❰ Range: 3300—33FF ❱ |author=Unicode Consortium |author-link=Unicode Consortium |date=2019 |website=Unicode.org}}

• Orders of magnitude (data)
• Binary prefix

{{Reflist}}

• http://physics.nist.gov/cuu/Units/binary.html
• http://www.quinion.com/words/turnsofphrase/tp-kib1.htm {{Webarchive|url=https://web.archive.org/web/20040612044148/http://www.quinion.com/words/turnsofphrase/tp-kib1.htm |date=12 June 2004 }}
• https://www.nist.gov/public_affairs/techbeat/tb9903.htm {{Webarchive|url=https://web.archive.org/web/20160820141603/http://www.nist.gov/public_affairs/techbeat/tb9903.htm |date=20 August 2016 }}

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Category:Units of information