[1] In the International System of Units (SI) the metric prefix kilo means 1,000 (103); therefore, one kilobyte is 1000 bytes.
[2] This definition, and the related definitions of the prefixes mega (1,000,000), giga (1,000,000,000), etc., are most commonly used for data transfer rates in computer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of most storage media, particularly hard disk drives,[3] flash-based storage,[4] and DVDs.
[5][6][7] The usage of the metric prefix kilo for binary multiples arose as a convenience, because 1024 is approximately 1000.
The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letter K. The B is sometimes omitted in informal use.
In December 1998, the IEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024.