Units
Why does a 256 GB SSD show 238 GB?
238.4GB in Windows
for a drive sold as 256 GB: the same bytes, counted in powers of 1,024
The same decimal-versus-binary difference: the SSD holds 256 billion bytes, which is 238.4 gibibytes. Windows shows the second number with a "GB" label.
The arithmetic
- 256 GB = 256,000,000,000 bytes (the maker's decimal count)
- 1 GiB = 1,024 × 1,024 × 1,024 = 1,073,741,824 bytes
- 256,000,000,000 ÷ 1,073,741,824 = 238.42 GiB
- The number looks 6.9 % smaller, with every byte still there
| Sold as | Windows shows | Looks smaller by |
|---|---|---|
| 16 GB | “14.9 GB” | 6.9 % |
| 32 GB | “29.8 GB” | 6.9 % |
| 64 GB | “59.6 GB” | 6.9 % |
| 128 GB | “119.2 GB” | 6.9 % |
| 256 GB | “238.4 GB” | 6.9 % |
| 512 GB | “476.8 GB” | 6.9 % |
| 1 TB | “931.3 GB” | 6.9 % |
| 2 TB | “1.81 TB” | 9.1 % |
| 4 TB | “3.63 TB” | 9.1 % |
| 8 TB | “7.27 TB” | 9.1 % |