Great Article: http://www.howtogeek.com/123268/windows-hard-drive-wrong-capacity/

My article is only meant to compliment it with extra numbers.

Why Drive Manufacturers Misrepresent their drive sizes?  They make more money. They provide less storage for same price (I might be wrong on the price and maybe they dont make more money – they might be pricing it accordingly, but im not sure, either way we are still cheated on our space)

Why drive sizes are misrepresneted by drive manufacturers:

Bytes are 8 bits no matter what (for drive manuafcatures and for normal people)
but after that bytes: kilobytes and gigabytes and terabytes take a new meaning

For people and computers a kilobyte has 1024 bytes, and a megabyte has 1024 kilobytes and so on. In fact the proper term here is not kilobyte but kibibyte, and mebibyte and gibibyte and tebibyte. This is BASE 2.

However drive maanufactures use kilobyte is 1000 bytes, and a megabyte is 1000 kilobytes and so on. The proper terms are as we use kilobyte megabyte etc… This is BASE 10

Also note the more conversions you do the more space you lose, the more the drive manufacturer make. So back in the day if you bought 1 MB and only got 1000000 bytes isntead of 1024*1024=1048576 bytes. So we lost 48576.

However with drives as big as 4 TB. We lose alot more and drive manufacturer makes more.
4 TB is 4,000,000,000,000 bytes but should be 4,398,046,500,000 bytes. So we lose a good amount. 398,046,500,000 bytes which is 370.7 gigabytes (base2)

But what we see is in the computer when we plug in a 4TB drive is
4,000,000,000,000 / 1024 /1024 /1024 / 1024 = 3.64 TB

Now imagine 4 Drives in a RAID5 box:
4,000,000,000,000 * 3 (data drives, one drive lost to parity) = 12,000,000,000,000 bytes
So we see: 12,000,000,000,000 / 1024 / 1024 / 1024 / 1024 = 10.9 TB base 2
If drive manufacturers didnt lie we would have this many bytes:
(What were cheated out of) = (What we should get) – (What we get) =

13,194,100,000,000 bytes – 12,000,000,000,000 bytes =
1,194,100,000,000 bytes = 1,194,100,000,000 / 1024 / 1024 / 1024 / 1024 =
1.08 Tetabytes BASE 2 (Thats a full TB lost due to lies)

Or imagine 12 Drives in a RAID5 box (bad setup should have RAID6 due to likelyness of losing a drive, anyhow…):
4,000,000,000,000 * 11 (one lost to parity as well) = 44,000,000,000,000 bytes
So we see: 44,000,000,000,000 / 1024 / 1024 / 1024 / 1024 = 40.01 TB BASE 2
If drive manufacturers didnt lie we would have this many bytes:
(What were cheated out of) = (What we should get) – (What we get) =
48,378,500,000,000 bytes – 44,000,000,000,000 bytes =
4,378,500,000,000 bytes = 4,378,500,000,000 / 1024 / 1024 / 1024 / 1024 =
3.98 Terabytes BASE 2 (Thats alot of space lost to drive manufacturer lies/conventions)