More and more, I’m seeing the Ki, Mi, etc. set of unit prefixes used, but with little mention of any sort of uniform interpretation of them.

The question, if you don’t know, is about what these prefixes mean. In the computer world, the prefixes traditionally represented the sequence of values for (210)n, where n is greater than zero, so 1 kB was (210)1 → 1,024 bytes, 1 MB was (2010)2 → 1,048,576 bytes, and so on. This is a problem because the SI defines those prefixes as the sequence of values for (103)n, so 1 kg is (103)1 → 1,024 grams and 1 Mg → 1,000 kg → 1,000,000 grams.

So, how do Ki, Mi, etc. fit into all of this? IEEE-SA approved proposal P1541 as a trial-use standard for the duration of two years. Sure, the end of that two year period is in a couple of weeks, but if the convention is catching on, likely something more will come of it. You can order 1541-2002 IEEE Standard for Prefixes for Binary Multiples from IEEE, and there’s a bunch of other links to who else is formally adopting it here

So, when someone talks about MiB or GiB of storage, they aren’t just totally making up terms.1 Now, to remember that the correct capitalization of 1,024 bytes is 1 KiB, even though 1000 bytes is 1 kB.

  1. although they might be a standards wonk [↩]

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