Kibibyte

The kibibyte is a multiple of the unit byte for quantities of 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]

Multiples of bytes
Decimal
Value Metric
1000 kBkilobyte
10002 MBmegabyte
10003 GBgigabyte
10004 TBterabyte
10005 PBpetabyte
10006 EBexabyte
10007 ZBzettabyte
10008 YByottabyte
Binary
Value IEC JEDEC
1024 KiBkibibyte KBkilobyte
10242 MiBmebibyte MBmegabyte
10243 GiBgibibyte GBgigabyte
10244 TiBtebibyte
10245 PiBpebibyte
10246 EiBexbibyte
10247 ZiBzebibyte
10248 YiByobibyte

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]

Definition

1 kibibyte (KiB) = 210 bytes = 1024 bytes

It follows from this definition, and from the definition of mebibyte (MiB) as 220 bytes that

1024 kibibytes = 1 mebibyte

The prefix kibi is derived as a portmanteau of 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]

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

1 kibibyte = 8192 bits

History

The kibibyte is closely related to the kilobyte. The latter term is often used in some contexts as a synonym for kibibyte, but formally refers to 103 bytes = 1000 bytes, as the prefix kilo is defined in the International System of Units.

The binary interpretation of the metric prefixes causes relatively small differences with the smallest prefixes in the series, i.e. for kilo and mega, but grows to substantial differences beyond.

Donald Knuth proposed to call this unit a large kilobyte (KKB).[6]

In product advertising and other non-scientific publications, "kilobyte" sometimes refers to a power of ten and sometimes a power of two.[7][8][9]