The kilobyte (symbol: kB)1 is a multiple of the unit byte for digital information. Historically and in common usage a kilobyte refers to 1024 (210) bytes in most fields of computer science and information technology.234 However hard disk drives measure capacity in strict accordance with the rule of the International System of Units unit prefixes (prefixes like kilo- and mega-) that are based on decimal math.56 In such mass storage contexts megabyte equals precisely 1000000 bytes and gigabyte is precisely 1000 times greater than a megabyte. This association suggests that kilobyte can also denote 1000 bytes in the context of mass storage. Thus kilobyte and its symbol KB can be ambiguous their exact value (1024 or 1000) dependent upon context.

In December 1998 an international standards organization attempted to address these dual definitions of the conventional prefixes by proposing unique binary prefixes and prefix symbols to denote multiples of 1024 such as kibibyte (KiB) which exclusively denotes 210 or 1024 bytes.7 Had this proposal been widely and consistently adopted it would have liberated the standard unit prefixes to unambiguously refer only to their strict decimal definitions wherein kilobyte would be understood to represent only 1000 bytes. However in the over12 years that have since elapsed the proposal has seen little adoption by the computer industry.891011 See also Kibibyte Data rate units data References Note that lowercase k is the proper unit symbol for the prefix kilo. Uppercase K is properly the unit symbol for the unit of thermodynamic temperature kelvin. Moreover the rule of the International System of Units (the SI) is that when describing the magnitude of a measure a space always separates the numeric value of a quantity and its unit symbol e.g. 1 kB. Nonetheless it is exceedingly common within the computing industry when denoting binary capacityparticularly in marketing literature and product packagingto use uppercase K and no space (1KB) although 1 KB is not incorrect and is often considered more suitable in technical writing. definition of kilobyte from Oxford Dictionaries Online. Askoxford.com. Retrieved on 2011-01-07. Kilobyte Definition and More from the Free Merriam-Webster Dictionary. Merriam-webster.com (2010-08-13). Retrieved on 2011-01-07. Kilobyte Define Kilobyte at Dictionary.com. Dictionary.reference.com (1995-09-29). Retrieved on 2011-01-07. Drive displays a smaller capacity than the indicated size on the drive label i.e. see HGST Samsung Seagate Toshiba and Western Digital websites National Institute of Standards and Technology. "Prefixes for binary multiples". http://physics.nist.gov/cuu/Units/binary.html.  "In December 1998 the International Electrotechnical Commission (IEC) ... approved as an IEC International Standard names and symbols for prefixes for binary multiples for use in the fields of data processing and data transmission." Upgrading and Repairing PCs Scott Mueller Pg. 596 ISBN 0789729741 The silicon web: physics for the Internet age Michael G. Raymer Pg. 40 ISBN 9781439803110 Knuth: Recent News. Cs-staff.stanford.edu. Retrieved on 2011-01-07. Atwood Jeff. (2007-09-10) Gigabyte: Decimal vs. Binary. Coding Horror. Retrieved on 2011-01-07. v d eUnits of information Base units Bit  Byte Related units Nibble  Word  Octet Traditional bit units Kilobit  Megabit  Gigabit  Terabit  Petabit  Exabit  Zettabit  Yottabit Traditional byte units Kilobyte  Megabyte  Gigabyte  Terabyte  Petabyte  Exabyte  Zettabyte  Yottabyte IEC bit units Kibibit  Mebibit  Gibibit  Tebibit  Pebibit  Exbibit  Zebibit  Yobibit IEC byte units Kibibyte  Mebibyte  Gibibyte  Tebibyte  Pebibyte  Exbibyte  Zebibyte  Yobibyte