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    $\begingroup$ The consensus seems to be that disk size is the nearest simple approximation lower than n×1000^m. So 2.057×10^12 bytes would be advertised as 2 TB, not 2.1 TB. $\endgroup$
    – l0b0
    Commented Mar 9, 2018 at 20:15
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    $\begingroup$ I'd note the prefixes rarely (basically never) have their binary meaning with units other than bytes. A megapixel is 1 million pixels, a megabit is a million bits. $\endgroup$
    – cHao
    Commented Mar 12, 2018 at 19:51
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    $\begingroup$ The filesystem megabyte being $2^{20}$ bytes - maybe. Sometimes in the same OS you'll see "megabytes" (including decimal precision) being $10^6$ in some of the tools and $2^{20}$ in others. Most often in command line tools vs GUI tools, but I know of an OS where even different OS-provided GUI tools disagree on this... $\endgroup$
    – davidbak
    Commented Mar 17, 2018 at 2:31
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    $\begingroup$ @davidbak is right. It depends on OS also. In 2009, Apple switched to standards-based prefixes for filesystems etc, to match disk drive manufacturers, i.e. GB = 10^9 bytes. eshop.macsales.com/blog/… Ubuntu changed in 2010 wiki.ubuntu.com/UnitsPolicy When will Windows catch up with reality? $\endgroup$
    – nealmcb
    Commented Mar 10, 2021 at 21:11
  • $\begingroup$ @nealmcb I'm glad I'm not the only one who's been ticked off by this. I've always found it odd when Windows displayed something like 100.71 MB (105,600,322 bytes) and was never able to figure out why this was the case until I learned about the whole fiasco with binary vs. decimal units. $\endgroup$
    – user14314
    Commented Mar 12 at 11:11