Have you ever wondered why computers always indicate that your hard drive or memory card has a smaller storage capacity than what’s advertised on the box (and the card itself)? No, it’s not because you got a defective card, it’s not because your card came preloaded with a bunch of unwanted files (your hard drives, maybe), and it’s not because the manufacturers are cheating you by skimping out on the storage space (well, not directly, at least). The reason has to do with math and marketing. But our question is, why the stated capacity of the drive can’t be usable?

So here is the answer. There are 3 different reasons behind it:

# Reason 1

Different operating systems treat your disk differently. Windows OS may not show the disk space like Linux, Mac or Unix. There are little discrepancies between the file formats and algorithms used by different operating systems. (It doesn’t matter much).

# Reason 2

Another reason is that- A portion of memory space is reserved for system files and data sector for better performance. This is the primary reason behind the less usable space than the mentioned space.

# Reason 3

The last reason but not the least(actual logical reason) is the calculation method used by the disk manufacturing companies. Humans think about numbers in base 10, the decimal numeral system, because we have 10 fingers and 10 toes. That’s why the parts of numbers are called “digits” — just like the parts of our hands and feet.

Computers, on the other hand, think in base 2, the binary numeral system. They consider 1 KB = 1000 Bytes. But your OS may consider it as 1 KB = 1024 KB. Here you are also losing a considerable amount of disk space.

Look at the calculation below:

 Virtual Storage Disk Storage 1 MB = 1024 KB 1 MB = 1000 KB 1 GB = 1024 MB 1 GB = 1000 MB 8 GB = 8192 MB 8 GB = 8000 MB 7.2 GB = 7372 MB 7.2 GB = 7200 MB

Herein lies the root of the issue. The “brilliant” marketing gurus at data storage companies decided early on that all their products should be marketed in the decimal system, since that’s what consumers understand.

Therefore, one megabyte on their products is equal to 1,000,000 bytes, and one gigabyte is equal to 1,000,000,000 bytes. To a computer, however, a megabyte is 1,048,576 bytes and a gigabyte is 1,073,741,824 bytes.

Take a close look at the box your hard drive or memory card came in, and you’ll notice asterisks. Look for the fine print, and you’ll see a disclaimer stating that the figures are stated in base 10: