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"MiB" redirects here. For similar abbreviations, see MIB (disambiguation).

The mebibyte is a multiple of the unit byte for digital information.[1] The binary prefix mebi means 220, therefore one mebibyte is equal to 1048576bytes. The unit symbol for the mebibyte is MiB.

The unit was established by the International Electrotechnical Commission (IEC) in 1998.[2] It was designed to replace the megabyte, which is still being used in many contexts to represent 220 bytes, which is incompatible with the definition of the prefix mega in the International System of Units (SI) as a multiplier of 106.

The binary prefixes have been accepted by all major standards organizations and are part of the International System of Quantities.[3] Many GNU/Linux distributions utilize the unit, but it is not yet widely published within the industry or media.[4][5][6][7]

Multiples of bytes
Value IEC
1000 (103) kB (kilobyte)
10002 (106) MB (megabyte)
10003 (109) GB (gigabyte)
10004 (1012) TB (terabyte)
10005 (1015) PB (petabyte)
10006 (1018) EB (exabyte)
10007 (1021) ZB (zettabyte)
10008 (1024) YB (yottabyte)
1024 (210) KiB (kibibyte) KB (kilobyte)
10242 (220) MiB (mebibyte) MB (megabyte)
10243 (230) GiB (gibibyte) GB (gigabyte)
10244 (240) TiB (tebibyte)
10245 (250) PiB (pebibyte)
10246 (260) EiB (exbibyte)
10247 (270) ZiB (zebibyte)
10248 (280) YiB (yobibyte)


1 MiB = 220 bytes = 1024 kibibytes = 1048576bytes

The prefix mebi is a binary prefix derived from the words mega and binary, indicating its origin in the closeness in value to the SI prefix mega. One mebibyte (MiB) is 220, i.e. 1024 x 1024 bytes,[8] or 1048576bytes.

Despite its official status, the unit mebibyte is not commonly used even when reporting byte counts calculated in binary multiples, but is often represented as megabytes. Formally, one megabyte means 1000 x 1000 bytes. Disk drive manufacturers strictly use decimal units, and the megabyte means 1000000bytes. The discrepancy may cause confusion, since operating systems using the binary method report lower numerical values for storage size than advertised by manufacturers. Many operating systems compute file size in mebibytes, but report the number as MB. For example, all versions of the Microsoft Windows operating system show a file of 220 bytes as "1.00 MB" or "1,024 KB" in its file properties dialog and show a file of 106 (1000000) bytes as 976 KB.

All versions of Apple's operating systems had the same behavior until Mac OS X version 10.6, which instead uses megabytes for all file and disk sizes, so it reports a 106 byte file as 1 MB.[9][10]

The Ubuntu developer Canonical implemented an updated units policy in 2010 and as of Ubuntu 10.10 all versions now adhere to the IEC binary prefix for base-2 units and the SI prefix for base-10 units. [11]


The binary prefix mebi was defined by the International Electrotechnical Commission (IEC) in December 1998. The use of the binary prefixes to replace metric prefixes has been endorsed by all major international standards bodies.[citation needed]

The mebibyte is closely related to the megabyte. The latter term is often used as a synonym for mebibyte, but it formally refers to 1000 kilobytes, or 1,000,000 bytes. The binary prefix mebi, which is a factor of 220, was created to provide an unambiguous unit that is distinct from the metric SI prefix mega (M). Binary prefixes are becoming more predominant in scholarly literature, descriptions of computer hardware and open source software.[12][13]

See also[edit]


  1. ^ International Electrotechnical Commission (January 2010). "IEC 60050 - International Electrotechnical Vocabulary - Details for IEV number 112-01-27". Retrieved 2011-06-19. 
  2. ^ International Electrotechnical Commission (January 1999), IEC 60027-2 Amendment 2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.[1]
  3. ^ "IEC 80000-13:2008". International Organization for Standardization. Retrieved 21 July 2013. 
  4. ^ Upgrading and Repairing PCs, Scott Mueller, Pg. 596, ISBN 0-7897-2974-1
  5. ^ The silicon web: physics for the Internet age, Michael G. Raymer, Pg. 40, ISBN 978-1-4398-0311-0
  6. ^ Knuth: Recent News. Retrieved on 2011-01-07.
  7. ^ Atwood, Jeff. (2007-09-10) Gigabyte: Decimal vs. Binary. Coding Horror. Retrieved on 2011-01-07.
  8. ^ "Definition of NIST binary". Ziff-Davis. 2010. Retrieved 2010-07-31. 
  9. ^ "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16. 
  10. ^ David Pogue (2011), Mac OS X Lion: The Missing Manual Missing Manual, Oreilly Series, O'Reilly Media, pp. 473–474, ISBN 978-1-4493-9749-4 
  11. ^ "Ubuntu UnitsPolicy". Ubuntu. 2010. Retrieved 2013-09-26. 
  12. ^ HDD Turns 50 Years Today - The Chronicles
  13. ^ Backman, R. B. (2004). The Description, Evolution, and Applications of Binary Prefixes.