- Just bought new Hard Disk Drive with Labeled Capacity 500GB but your computer shows only 465.66 GB!!!

- Why a hard drive's capacity often appears to be less than advertised label when showing in Microsoft Windows (My Computer) or Apple Mac (Disk Utility) ?!

- Need to explain to your clients how much they will get when they they purchase new 4TB Hard Disk Drive.

It all comes down to Binary and Decimal numbering, to Bits and Bytes,...

Manufacturers calculate drive capacity slightly differently than how computers actually see usable storage space.
Manufacturers count drive capacity using the decimal system, while computers count drive capacity using the binary system, so, when you wish to convert to one system of measurement to another, there are discrepancies.

Use this simple program to calculate actual hard disk drive capacity from advertised (market) one.