A 1 TB drive holds 931.32 GiB, which Windows displays as "GB"; a 500 GB drive shows 465.66.
| Size (decimal) | Bytes | Same size in binary units | Binary shows less by |
|---|---|---|---|
| 1 KB | 1,000 | 0.98 KiB | 2.3% |
| 100 KB | 100,000 | 97.66 KiB | 2.3% |
| 500 KB | 500,000 | 488.28 KiB | 2.3% |
| 1 MB | 1,000,000 | 0.95 MiB | 4.6% |
| 100 MB | 100,000,000 | 95.37 MiB | 4.6% |
| 500 MB | 500,000,000 | 476.84 MiB | 4.6% |
| 1 GB | 1,000,000,000 | 0.93 GiB | 6.9% |
| 8 GB | 8,000,000,000 | 7.45 GiB | 6.9% |
| 16 GB | 16,000,000,000 | 14.90 GiB | 6.9% |
| 32 GB | 32,000,000,000 | 29.80 GiB | 6.9% |
| 64 GB | 64,000,000,000 | 59.60 GiB | 6.9% |
| 128 GB | 128,000,000,000 | 119.21 GiB | 6.9% |
| 256 GB | 256,000,000,000 | 238.42 GiB | 6.9% |
| 500 GB | 500,000,000,000 | 465.66 GiB | 6.9% |
| 512 GB | 512,000,000,000 | 476.84 GiB | 6.9% |
| 1 TB | 1,000,000,000,000 | 0.91 TiB | 9.1% |
| 2 TB | 2,000,000,000,000 | 1.82 TiB | 9.1% |
| 4 TB | 4,000,000,000,000 | 3.64 TiB | 9.1% |
| 8 TB | 8,000,000,000,000 | 7.28 TiB | 9.1% |
| 16 TB | 16,000,000,000,000 | 14.55 TiB | 9.1% |
| 20 TB | 20,000,000,000,000 | 18.19 TiB | 9.1% |
| 1 PB | 1,000,000,000,000,000 | 0.89 PiB | 11.2% |
How it is computed
Decimal units step by 1,000 (1 GB = 10⁹ bytes); binary units step by 1,024 (1 GiB = 2³⁰ bytes). The gap grows with each prefix: about 2.3% at kilo, 6.9% at giga, 9.1% at tera.
FAQ
Why does my new drive show less space than advertised?+
Manufacturers count in decimal GB and TB; Windows counts in binary units but labels them GB. No space is missing, only the unit differs.
Does macOS do the same?+
No. Since 2009 macOS reports decimal units, so a 1 TB drive shows about 1 TB, minus formatting overhead.