What is a Kibibyte?

If there are eight bits in a byte, how many bytes are there in a kilobyte? If you’re familiar with computers, you might say 1,024, while someone who is less so may say 1,000. Who is right?

Surprisingly, the person who answered 1,000 would be correct.

Historically, there were 1,024 bytes in a kilobyte. That created a problem, though. The Latin-derived kilo, mega and giga prefixes refer to base-ten numbers, which means using them for binary denominations would conflict with the SI/metric system. So in 1999 the International Electrotechnical Commission defined the kilobyte and its siblings as being base ten, introducing a new system for binary units.

Enter the kibibyte.

A kibibyte (abbreviated as KiB) is 1,024 bytes. The equivalent to a megabyte (106) is the mebibyte (220) and the gigabyte (109) is the gibibyte (230).

What does this mean for you? Nothing, probably. Unless you’re doing some programming work where specificity is very important, or dealing with very large amounts of data, measuring data in base ten is perfectly sensible. Hard disk manufacturers have been doing it for years, and some operating systems now even use base ten units. Apple has done it since Snow Leopard (OS X 10.6), though I think Microsoft may still use base two while labeling the numbers incorrectly. Most Linux distributions use base two, though they usually label the values with the proper suffix.

Anyway, it’s certainly interesting. It reminds me of another bit of numerical confusion. Network speeds are usually measured and advertised in megabits per second, as bytes aren’t really relevant to the “tubes,” and its not uncommon for sub-byte chunks of data to be sent down the line. Meanwhile, a lot of software displays the speed of downloads in megabytes per second instead. This creates confusing situations occasionally. (Convention is to use a lower-case “m” for megabits and a capital one for megabytes.)