When you’re buying memory, a KB is 1024 bytes, a MB is 1024 KB, and a GB is 1024 MB. However, manufacturers of RAM don’t sell it in even groups of 1000 – they use groups of 1024. The hard disk manufacturer thus advertises the disk as a 500 GB hard disk. To a hard disk manufacturer, one KB is 1000 bytes, one MB is 1000 KB, and one GB is 1000 MB. There’s also some overhead required when Windows formats your drive, for the file system and boot data, though in comparison to today’s large hard drives, it’s not a lot. The reason for this difference lies in the way hard drive manufacturers advertise their devices, versus the way Windows computers actually use the storage devices.
If you’ve paid attention to hard drives, USB flash drives, and other storage devices, you may have noticed that they always have less space than promised once they’re formatted. Why Your Hard Drive Shows Less Space Than Advertised
