Why does my hard drive report less capacity than indicated on the drive’s label? We may measure a kilobyte as 1,000 bytes but Windows refers to a kilobyte as 1,024 bytes and a megabyte as 1,024 kilobytes and a gigabyte as 1,024 megabytes. That means the actual amount of space on the drive is going to be lower than what you’re told, with the difference being bigger as you get to bigger drives. Its just mathematics. Therefore for each gigabyte reported , you’ll have about 70MB less space when you plug it in which means that your 1TB drive has closer to 900GB as measured by Windows. Also : Looking at the picture above is a true indication of how delicate hard drives are and think about what can happen if you drop it.