Reference
SI Decimal Prefixes and Binary Prefixes
Kilo, mega, and giga versus kibi, mebi, and gibi, and why a 1 TB drive reports less than 1 TiB.
SI prefixes are decimal powers of ten: kilo (10³), mega (10⁶), and giga (10⁹). Binary prefixes are powers of two: kibi (2¹⁰), mebi (2²⁰), and gibi (2³⁰). Storage sold in decimal gigabytes but reported by a binary-based operating system shows a smaller number for the same bytes.
| Decimal | Value | Binary | Value |
|---|---|---|---|
| kilo (k) | 10³ | kibi (Ki) | 2¹⁰ = 1024 |
| mega (M) | 10⁶ | mebi (Mi) | 2²⁰ = 1 048 576 |
| giga (G) | 10⁹ | gibi (Gi) | 2³⁰ = 1 073 741 824 |
01Limitations
The binary prefixes are standardized, but consumer labels and older software may still use the decimal symbols for binary values, so check the convention before comparing capacities.
Sources
- The International System of Units (SI Brochure) — BIPM (accessed 2026-09-27)
- SI Units — NIST — NIST (accessed 2026-09-27)