SI unit prefixes (nano to tera)
These prefixes attach to SI base units (m, g, s, …) and many derived units.
| Prefix | Symbol | Factor | Power |
|---|---|---|---|
| nano | n | 0.000000001 | 10⁻⁹ |
| micro | µ | 0.000001 | 10⁻⁶ |
| milli | m | 0.001 | 10⁻³ |
| centi | c | 0.01 | 10⁻² |
| deci | d | 0.1 | 10⁻¹ |
| (none) | — | 1 | 10⁰ |
| deka | da | 10 | 10¹ |
| hecto | h | 100 | 10² |
| kilo | k | 1000 | 10³ |
| mega | M | 1 000 000 | 10⁶ |
| giga | G | 1 000 000 000 | 10⁹ |
| tera | T | 1 000 000 000 000 | 10¹² |
| peta | P | 10¹⁵ | 10¹⁵ |
Notes
- Symbol case matters: m = milli, M = mega.
- Binary prefixes (Ki, Mi, Gi) are separate — see data storage units.
Frequently asked questions
- What is the difference between milli and mega?
- Milli (m) means one thousandth, 10⁻³, while mega (M) means one million, 10⁶ — the case of the symbol alone changes the factor by nine orders of magnitude.
- How many millimeters are in a kilometer?
- A kilometer is 10³ meters and a millimeter is 10⁻³ meters, so one kilometer equals 1,000,000 millimeters (10⁶ mm).
- What do the SI prefixes from nano to tera mean?
- Nano = 10⁻⁹, micro = 10⁻⁶, milli = 10⁻³, centi = 10⁻², deci = 10⁻¹, deka = 10¹, hecto = 10², kilo = 10³, mega = 10⁶, giga = 10⁹, tera = 10¹² (and peta = 10¹⁵).