Reference sheet
SI prefixes chart
The 24 SI prefixes adopted by the CGPM (ronna, quetta, ronto and quecto were added in 2022). Prefixes multiply SI units by a power of ten: 1 kN = 1 000 N, 1 µm = 0.000 001 m.
| Prefix | Symbol | Power of ten | Decimal value |
|---|---|---|---|
| quetta | Q | — | |
| ronna | R | — | |
| yotta | Y | — | |
| zetta | Z | — | |
| exa | E | — | |
| peta | P | — | |
| tera | T | 1,000,000,000,000 | |
| giga | G | 1,000,000,000 | |
| mega | M | 1,000,000 | |
| kilo | k | 1,000 | |
| hecto | h | 100 | |
| deca | da | 10 | |
| deci | d | 0.1 | |
| centi | c | 0.01 | |
| milli | m | 0.001 | |
| micro | µ | 0.000001 | |
| nano | n | 0.000000001 | |
| pico | p | 0.000000000001 | |
| femto | f | — | |
| atto | a | — | |
| zepto | z | — | |
| yocto | y | — | |
| ronto | r | — | |
| quecto | q | — |
Tips
- Symbols are case-sensitive: m (milli) vs M (mega), p (pico) vs P (peta).
- Type u for µ (micro) when your keyboard has no µ key; Unitglide accepts both.
- Never stack prefixes: write ns, not mµs. The kilogram takes prefixes on the gram (mg, not µkg).
- Binary prefixes (Ki, Mi, Gi) are IEC, not SI: 1 KiB = 1 024 bytes.
Unitglide · unitglide.app/reference/si-prefixes · Factors from NIST SP 811, NIST Handbook 44 and the BIPM SI Brochure (9th ed.). Values rounded to 7 significant figures unless exact.