kB

kB is an abbreviation for kilobyte, a unit of information size. It commonly represents either 1,000 bytes (decimal) or 1,024 bytes (binary), with the latter arising from the historical use of powers of two in computing. The uppercase B distinguishes bytes from bits, since lowercase b denotes a bit. Because of mixed usage, the term kB can be ambiguous in practice.

To reduce confusion, formal prefixes were introduced by the International Electrotechnical Commission: kibibyte (KiB) for 1,024 bytes, mebibyte (MiB) for 1,048,576 bytes, and so on. Despite these standards, many software programs, operating systems, and hardware vendors continue to use kB to mean 1,024 bytes in contexts like memory sizes or file sizes, while storage devices are often marketed using decimal kilobytes of 1,000 bytes.

Usage examples vary: a small text file might be about 4 kB in decimal terms, or 4,096 bytes if interpreted binarily. Data transfer rates are sometimes given in kilobytes per second (kB/s), which may reflect decimal or binary conventions depending on the system or vendor.

In summary, kB denotes kilobyte and must be interpreted with attention to context, particularly whether decimal (1 kB = 1,000 bytes) or binary (1 kB ≈ 1,024 bytes) conventions are intended. For precise specification, KiB is preferred when 1,024 bytes are meant. See also byte, bit, kibibyte, kilobyte, mebibyte.