size_format() Displaying Incorrect Unit

[brashell]

The size_format() function is using binary standards for displaying a human readable version of the file size, shouldn’t we use the IEC standard of KiB, MiB etc for the unit, or convert to SI and use 1000 instead of 1024 as the value of bytes in a kB etc (ref: ​http://en.wikipedia.org/wiki/Kilobyte)? It was even noted that it was technically incorrect in the comments of the function: https://core.trac.wordpress.org/browser/tags/4.1/src/wp-includes/functions.php#L194 (If we do fix it, we need to take into consideration the whitespace in front of the 'B ' fixed in: [31052])

[brashell]

Changeset [31052], ticket #30908

[dd32]

I vaguely recall this coming up in the past, but couldn't find any tickets for it.

Some history of the KB vs KiB debate is in Wikipedia: ​http://en.wikipedia.org/wiki/Mebibyte#Definition which shows that until 2009/2010ish all major OS's displayed 1024B as 1KB, completely ignoring the IEC spec, so we followed along and used what everyone expects.
However, now OS X and Ubuntu (at least) have switched to using 1000B = 1KB, leaving Microsoft the hold-out of ignoring the IEC standard.

This is so minor that it can go either way to me, but if we do change anything, we should replace 1024 with 1000, just so we never have to display 'KiB' since that's even more unfamiliar to people. I doubt anyone would notice or complain that their website says the file is 2% larger than it really is, especially not with the filesizes most people upload.

[Otto42]

At least one case exists where a user assumed that their images were being compressed on upload because of the displayed filesize difference between the reading in the Media Library vs. what their OS is telling them:

​https://wordpress.org/support/topic/stop-wp-compressing-images-to-90-on-uploading-to-media-library

[SergeyBiryukov]

Related: #37037