MB vs. MiB: Identify Decimal and Binary Data Units
By Convert Calc Editorial Team · Published · Updated
Two amounts with similar labels can represent different byte counts. Start with the original specification’s definition, then choose the matching unit in the data calculator. Do not infer the definition from a particular operating system or from whether the number describes memory or storage.
Decimal and binary definitions
Decimal prefixes use powers of 1000: 1 kB = 1000 bytes, 1 MB = 1000000 bytes and 1 GB = 1000000000 bytes. Binary prefixes have distinct names: 1 KiB = 1024 bytes, 1 MiB = 1048576 bytes and 1 GiB = 1073741824 bytes. NIST’s binary-prefix reference supplies these comparisons and the relationship 1 byte = 8 bits. The BIPM prefix table supplies decimal powers and symbols.
This site’s decimal-named routes use decimal factors. Earlier versions used binary factors under MB/GB-style labels; the calculator now offers explicit KiB/MiB/GiB/TiB/PiB choices for binary amounts. Check the convention when interpreting a historical result.
Work a capacity example
Suppose a stated capacity is exactly 1000000000000 bytes. This is 1 decimal TB. To express the same amount in GiB, divide by the bytes per GiB:
1024³ = 1073741824
1000000000000 / 1073741824 ≈ 931.3226 GiBThis is a unit re-expression before filesystem metadata, reserved capacity or stored files. It does not prove that a particular drive has that much usable space or that any observed discrepancy comes only from labeling.
Use the data calculator to select GB and GiB. The standalone GB-to-GiB pair is not currently published; the category calculator supports both units.
Compare like quantities
| Decimal amount | Byte count | Binary amount (rounded) |
|---|---|---|
| 1 kB | 1000 | 0.9765625 KiB |
| 1 MB | 1000000 | 0.9536743164 MiB |
| 1 GB | 1000000000 | 0.9313225746 GiB |
| 1 TB | 1000000000000 | 0.9094947018 TiB |
The byte counts follow the definitions; repeating results are rounded here to at most ten significant digits. Extra digits do not establish the precision of the original measurement. For decimal comparisons, 1 GB is 1000 MB; for binary comparisons, 1 GiB is 1024 MiB.
Amounts and rates
B and b distinguish bytes and bits in this calculator. Mb/s is megabits per second; MB is a data amount. A hypothetical 50 GB file contains 400000 Mb. At a sustained payload rate of 100 Mb/s it takes 4000 seconds, about 66.7 minutes. If 100 Mb/s is only a connection limit, treat that duration as an ideal lower bound; actual throughput and overhead can increase it.
See storage planning examples for the assumptions behind these calculations, unit systems for naming conventions and methodology for source and rounding scope.
Reviewed October 5, 2026. No product-specific capacity or operating-system convention is assumed.