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Multiples of bytes
Value Metric
1 B byte
1000 kB kilobyte
10002 MB megabyte
10003 GB gigabyte
10004 TB terabyte
10005 PB petabyte
10006 EB exabyte
10007 ZB zettabyte
10008 YB yottabyte
1 B byte B byte
1024 KiB kibibyte KB kilobyte
10242 MiB mebibyte MB megabyte
10243 GiB gibibyte GB gigabyte
10244 TiB tebibyte
10245 PiB pebibyte
10246 EiB exbibyte
10247 ZiB zebibyte
10248 YiB yobibyte

The kibibyte is a multiple of the unit byte for digital information. The binary prefix kibi means 210, or 1024; therefore, 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.[1]

The unit was established by the International Electrotechnical Commission (IEC) in 1998,[2] has been accepted for use by all major standards organizations, and is part of the International System of Quantities.[3] The kibibyte was designed to replace the kilobyte in those computer science contexts in which the term kilobyte is used to mean 1024 bytes. The interpretation of kilobyte to denote 1024 bytes, conflicting with the SI definition of the prefix kilo (1000), used to be common.[4]


The unit prefix kibi specifies multiplication by 210 (1024). It was derived as a portmanteau from the words kilo and binary, indicating its origin in the closeness in value to the SI prefix kilo (1000). While the SI prefix is written with lowercase (k), all IEC binary prefixes start with an uppercase letter.[5]

Therefore, the definition of the kibibyte is:

1 kibibyte (KiB) = 210 bytes = 1024 bytes.

The next larger unit of information in the sequence with IEC binary prefixes is the mebibyte (MiB) (220 bytes):

1024 kibibytes = 1 mebibyte.

IEC specification 80000-13 defines one byte as 8 bits (1 B = 8 bit). Therefore,

1 kibibyte = 8192 bits.


The kibibyte is closely related to the kilobyte, which equals 1000 bytes, as the prefix kilo is defined in the International System of Units.

Within the field of computer science, during the 1970s and 1980s, the term kilobyte generally meant 1024 bytes, but was sometimes used to mean 1000 bytes. When describing random access memory, kilobyte typically meant 1024 bytes, but when describing disk drive storage, kilobyte typically meant 1000 bytes.[6] The errors associated with this ambiguity are relatively small with the lower prefixes in the series, i.e. for kilo and mega, but grows to substantial differences beyond.

In 1995, to resolve this ambiguity, the International Union of Pure and Applied Chemistry's Interdivisional Committee on Nomenclature and Symbols proposed new prefixes kibi, mebi, etc for powers of 1024.[7][8] The kibi proposal was formally adopted by the International Electrotechnical Commission in December 1998, and published in January 1999.[9][10]

In 1999, Donald Knuth proposed to call the kibi unit a large kilobyte (KKB), but his proposal was not adopted.[11]

In spite of the formal adoption of the term kibibyte in 1999, the term "kilobyte" continues to be used to mean 1024 bytes in some product advertising and other non-scientific contexts.[12][13][14]

See also


  1. ^ International Electrotechnical Commission (2007). "Prefixes for binary multiples". Retrieved .
  2. ^ International Electrotechnical Commission (January 1999), IEC 60027-2 Amendment 2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics
  3. ^ "IEC 80000-13:2008". International Organization for Standardization. Retrieved .
  4. ^ "Definitions of the SI units: The binary prefixes". Retrieved .
  5. ^ National Institute of Standards and Technology. "Prefixes for binary multiples". Retrieved .
  6. ^ NIST "Prefixes for binary multiples"
  7. ^ IUCr 1995 Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS)
  8. ^ "Binary Prefix" University of Aukland Department of Computer Science
  9. ^ NIST "Prefixes for binary multiples"
  10. ^ Amendment 2 to IEC International Standard IEC 60027-2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.
  11. ^ "What is a kilobyte?". Retrieved .
  12. ^ "Safier vs WDC complaint". Archived from the original on October 16, 2007. Retrieved .
  13. ^ Grainger, Brian (7 August 2005). "I've got a bigger gigabyte than you!". Independent Computer Products Users Group (ICPUG). Retrieved .
  14. ^ Barry Wittman; Aditya Mathur; Tim Korb (30 December 2012). Start Concurrent: An Introduction to Problem Solving in Java with a Focus on Concurrency, 2013 Edition. Purdue University Press. p. 5. ISBN 978-1-55753-672-3. Retrieved 2013.

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