Two meanings of "gigabyte"
- Decimal (GB): 1 GB = 1,000,000,000 bytes. Drive makers, phone makers and macOS use this.
- Binary (GiB): 1 GiB = 1,073,741,824 bytes (1024 × 1024 × 1024). Windows counts this way but labels it "GB".
Why your drive looks smaller
A 1 TB drive holds 1,000,000,000,000 bytes. Divided by 1,073,741,824, that is about 931 binary gigabytes, so Windows shows "931 GB". Nothing is missing: the same number of bytes is being counted in a different unit. On a Mac, the same drive shows as 1 TB.
How big the gap gets
| Advertised | Shown by Windows |
| 128 GB | 119 GB |
| 256 GB | 238 GB |
| 512 GB | 476 GB |
| 1 TB | 931 GB |
| 2 TB | 1.81 TB |
Bits and bytes
Internet speeds are quoted in bits per second. There are 8 bits in a byte, so a 100 Mbps connection downloads at most 12.5 MB per second.
Convert any size
The Data Size Converter converts between bits, bytes, KB, MB, GB, TB and their binary KiB, MiB, GiB and TiB versions.