Mebibytes and Megabytes

(Or, why you should care and use the correct metric terminology.)

Okay, so what the heck does “MiB” mean? Shouldn’t it be just “MB”? Essentially, “MiB” stands for “Mebibyte” and “MB” stands for “Megabyte”. These two quantities are different. If you know about the metric system, you’ll recall that metric system prefixes tell you how many 10’s, 100’s or 1,000’s of units you’re talking about. If you’ve been paying attention to computing, you’ll have noticed that the “thousands” quantity that computer professionals generally use is not 1,000 exactly but 1,024, or 210. The Wikipedia article on Mebibyte is actually pretty informative on that score.So, if you’re going to be exact when you talk about file sizes, transfers and other things that happen in the computer world, you should be using the “Ki”, “Mi”, “Gi”, “Ti”, etc. previxes, not “K”, “M”, “G”, “T”.

But who cares?

The real answer here is that the Hard Drive Manufacturers care. Because when they’re using the thousands metric-style previxes, they’re actually practicing truth in advertising, and it works to their advantage. The reason this is so is that when a Hard Drive Manufacturer advertises a hard drive as 160 GB, what they mean is that the hard drive’s capacity is 160,000,000,000 bytes (152.6 GiB). What you are perhaps thinking is that the hard drive’s capacity is 160 GiB (i.e. 171,798,691,840 bytes). So you think you’re paying for approximately 7.5 GiB more than you’re getting. As the hard drive capacities in question keep going up, you’ll keep getting boned more and more, and the best part is that the Hard Drive Manufacturers are being completely accurate and truthful. It’s you who are doing the math/using the language wrong, so you can’t even think of suing anyone without looking like a just plain idiot.

So anyhow, I will be, when I can remember to be, pedantic, and try to use GB when I mean 1,000,000,000 bytes and GiB when I mean 230 bytes, and maybe you’ll get used to it and start using the units properly too.

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