The kibibyte and mebibyte and their ilk are ridiculous. Introduced in 1998, these units are related to each other by factors of 1,024, a number which is almost, but not quite the same as 1,000, the basis of the metric system. The only reason these units exist is to work around the ambiguity of some people using “kilobyte” to mean 1,000 bytes and others—understandably but unwisely—using “kilobyte” to mean 1,024 bytes. The sole advantage of the newfangled binary-based units is that they’re unambiguous: when someone says “kibibyte,” you know they really do mean that and not “kilobyte.”
For that reason, though, everyone should give measurements in kibibytes, mebibytes, and so on when at all possible. After a decade or two of such sanity maybe we’ll be able to ease back into using “kilobyte” when we mean “kilobyte” and not have to worry about being misinterpreted.