GB vs. MB vs. KB: How Data Storage Units Actually Work
How kilobytes, megabytes, gigabytes, and terabytes relate to each other, why 1,024 rather than 1,000 is used in computing, and why a drive's usable space looks smaller than advertised.
In computing, each data storage unit is 1,024 times the one below it: 1 kilobyte (KB) = 1,024 bytes, 1 megabyte (MB) = 1,024 KB, 1 gigabyte (GB) = 1,024 MB, and 1 terabyte (TB) = 1,024 GB. This is the binary convention operating systems typically use to report file and drive sizes.
Quick reference
| Unit | Equals | In bytes |
|---|---|---|
| 1 KB | 1,024 bytes | 1,024 |
| 1 MB | 1,024 KB | 1,048,576 |
| 1 GB | 1,024 MB | 1,073,741,824 |
| 1 TB | 1,024 GB | 1,099,511,627,776 |
Why your 1TB drive shows less than 1,000 GB
Storage manufacturers typically advertise capacity using the decimal (1,000-based) convention — a "1 TB" drive means 1,000,000,000,000 bytes. But your operating system reports free space using the binary (1,024-based) convention, so that same drive shows up as roughly 931 GB. Nothing is missing — it's the same number of bytes, described with two different conventions.
Bits vs. bytes
A byte is 8 bits. This distinction matters most for internet speeds, which are usually advertised in megabits per second (Mbps) rather than megabytes per second (MBps) — a "100 Mbps" connection tops out around 12.5 MB/s, not 100 MB/s.
Convert between bits, bytes, KB, MB, GB, TB, and PB instantly in the Unit Converter.