IECprefixes

IEC prefixes are a set of binary prefixes defined by the International Electrotechnical Commission to denote powers of two in information technology. They were created to provide unambiguous names for quantities expressed in bytes and other units when the base is 2, addressing long-standing confusion with the decimal SI prefixes that use powers of 10.

The prefixes and their recommended symbols are Ki (kibi), Mi (mebi), Gi (gibi), Ti (tebi), Pi (pebi), Ei (exbi), Zi (zebi), and Yi (yobi). They correspond to 2^10, 2^20, 2^30, 2^40, 2^50, 2^60, 2^70, and 2^80, respectively. When applied to units such as bytes, the conventional forms KiB, MiB, GiB, TiB, PiB, EiB, ZiB, and YiB are used. For example, 1 KiB equals 1024 bytes, and 1 GiB equals 1,073,741,824 bytes.

IEC prefixes are not SI prefixes, though they are recognized in international standards to reduce ambiguity with decimal prefixes like kilobyte (kB) and megabyte (MB), which in some contexts denote 1000 and 1,000,000 bytes. Usage of IEC prefixes varies by domain and software; some operating systems, standards bodies, and documentation adopt KiB, MiB, and the like, while others continue to use traditional abbreviations.

In practice, IEC prefixes improve precision in computing contexts such as memory sizes and data transfer rates, though their adoption is not universal. They remain a standard reference for distinguishing binary multiples from decimal multiples in technical communication.