Units
How many MB are in a GB?
1,000MB in a GB
and 1,024 MiB in a GiB. Decimal for drives, plans and macOS; binary for RAM and Windows.
Two answers are in everyday use, and both are 'right' in their own system. Decimal (SI): 1,000. Binary: 1,024. The binary units have their own names (MiB, GiB), which settle the question.
The arithmetic
- SI prefixes: kilo = 10³, mega = 10⁶, giga = 10⁹, so 1 GB = 10⁹ ÷ 10⁶ = 1,000 MB
- IEC binary prefixes: kibi = 2¹⁰, mebi = 2²⁰, gibi = 2³⁰, so 1 GiB = 2³⁰ ÷ 2²⁰ = 1,024 MiB
- Mixed: 1 GB = 1,000,000,000 ÷ 1,048,576 = 953.67 MiB
| Decimal | Bytes | Binary | Bytes | Binary is bigger by |
|---|---|---|---|---|
| kilobyte (KB) | 1,000 | kibibyte (KiB) | 1,024 | 2.4 % |
| megabyte (MB) | 1,000,000 | mebibyte (MiB) | 1,048,576 | 4.9 % |
| gigabyte (GB) | 1,000,000,000 | gibibyte (GiB) | 1,073,741,824 | 7.4 % |
| terabyte (TB) | 1,000,000,000,000 | tebibyte (TiB) | 1,099,511,627,776 | 10 % |
| petabyte (PB) | 1,000,000,000,000,000 | pebibyte (PiB) | 1,125,899,906,842,624 | 12.6 % |