File sizes in Windows not making sense

62,563 bytes are 61.0966797 kibibytes. The kibi prefix means that the base for calculation is 1024, bi standing for "binary" because 2^10 = 1024. It's only one of the binary prefixes, others being mebi or gibi.

A kilobyte on the other hand is 1000 bytes, using the classic SI prefixes that you know from kilometers and kilograms. It's using the decimal base, 10^3 = 1000, so Google is actually right. If you had googled for the same amount in kibibytes, you'd have gotten the right answer in computing terminology.

It's really important to make the distinction between kilo and kibi these days, and actually, Windows should report it as "61 KiB" to be absolutely precise. This is the IEC convention for making the distinction easier.

That being said, there's still a lot of ambiguity these days, where hard drive sizes are typically reported in binary units (but not always explicitly), and connection speeds are given in SI units.

Yeah, think of google as the Mad Hatter. You have to ask the right question. Or perhaps an Elf: Sometimes your answer will be both yes and no.

1KB = 1024 bytes. Thus:

62563 / 1024 = 61.097KB

As a shortcut many people and systems treat a KB as 1000 since Kilo is the SI prefix for 1000. Computer scientists however use the prefix for 2^10 which is 1024.

Most computer-related numbers use binary prefixes, in contrast to SI system which uses decimal prefixes. It means that:

• 1 kilogram = 10³ grams, but
• 1 kilobyte = 2¹⁰ bytes

That's respectively 1000 grams and 1024 bytes. 62563 / 1024 ~= 61, so Windows is right.

Not everything computer-related is based on binary prefixes, though, and this inconsistency often leads to misunderstandings. This Wikipedia page describes what prefixes are used for measuring different things.

One extreme case is bandwidth. It's typically using binary prefixes when expressed in bytes per second and decimal prefixes when expressed in bits per second. So this sentence is true:

1 byte per second = 8 bits per second

But this one is false:

1 kilobyte per second = 8 kilobits per second

Because:

• 1 KB/s = 1024 B/s
• 1 Kbps = 1000 bps

(related question)