Rant Two - Hard Drive Sizes

Through my academic career I've fancied myself a computer scientist who just hasn't gotten his degree yet because of all the red tape. However, after 5 years of being a professional student, the number of people in my classes that say a 500GB hard drive comes home with around 465GB because of "formatting" makes my brain hemorrhage. Sure, formatting can take up 35GB... if you're using FAT32. And unless you're using your phone's SD card as your primary hard drive, you're probably not using FAT32. "Ok asshole, where is the rest of my space then?". Quite frankly, it doesn't exist. When you buy a 500 gigabyte hard drive, you're getting just that, five hundred gigabytes. But computers don't use gigabytes. They use gibibytes. So, whats the difference?

SI decided that they were going to keep kilo, mega, giga, terra, etc., on powers of ten, but computers use powers of two. Powers of 2 increase three orders of magnitude every 10th integer; powers of 10 increase three orders of magnitude every 3rd integer. The following is a table of the powers of 2 alongside the powers of 10 that correspond to the SI prefixes. After that I will discuss the differences, the different prefixes for powers of two, and what that means when you pop that brand new hard drive into your computer.

Power of Two	Value	Binary Prefix	Power of Ten	Value	Decimal Prefix
2 ^ 10	1,024	Kibi (KiB)	10 ^ 3	1,000	Kilo (KB)
2 ^ 20	1,048,576	Mebi (MiB)	10 ^ 6	1,000,000	Mega (MB)
2 ^ 30	1,073,741,824	Gibi (GiB)	10 ^ 9	1,000,000,000	Giga (GB)
2 ^ 40	1,099,511,627,776	Tebi (TiB)	10 ^ 12	1,000,000,000,000	Tera (TB)

Now we can see the difference between the number of bytes in a gibibyte (GiB) and in a gigabyte (GB). There are 73,741,824 more bytes in a gibibyte than a gigabyte, and since your computer works with gibibytes not gigabytes, thats a big difference. So, when you buy a 500GB how many GiBs are you getting? Well, 500GB is 500,000,000,000 bytes, so divide that by 1,073,741,824 and you get 465.661287GiB. I am using a 500GB hard drive, and 465 GiB is what my computer tells me I have; and I'm using most of it. Not a whole lot of space used up for formatting huh?

If you have any questions, would like me to perform the calculation for another size of hard drive, or have any recommendations for this article, please leave a comment. :)