Kilo (k) multiplies a unit by 1,000 and mega (M) by 1,000,000; the SI now has 24 prefixes, from quecto (10⁻³⁰) to quetta (10³⁰).
| Prefix | Symbol | Factor | Decimal |
|---|---|---|---|
| quetta | Q | 10³⁰ | — |
| ronna | R | 10²⁷ | — |
| yotta | Y | 10²⁴ | — |
| zetta | Z | 10²¹ | — |
| exa | E | 10¹⁸ | — |
| peta | P | 10¹⁵ | — |
| tera | T | 10¹² | — |
| giga | G | 10⁹ | 1,000,000,000 |
| mega | M | 10⁶ | 1,000,000 |
| kilo | k | 10³ | 1,000 |
| hecto | h | 10² | 100 |
| deca | da | 10¹ | 10 |
| deci | d | 10⁻¹ | 0.1 |
| centi | c | 10⁻² | 0.01 |
| milli | m | 10⁻³ | 0.001 |
| micro | µ | 10⁻⁶ | 0.000001 |
| nano | n | 10⁻⁹ | 0.000000001 |
| pico | p | 10⁻¹² | — |
| femto | f | 10⁻¹⁵ | — |
| atto | a | 10⁻¹⁸ | — |
| zepto | z | 10⁻²¹ | — |
| yocto | y | 10⁻²⁴ | — |
| ronto | r | 10⁻²⁷ | — |
| quecto | q | 10⁻³⁰ | — |
How it is computed
Each prefix multiplies the unit by the power of ten shown, as defined by the BIPM. Ronna, quetta, ronto and quecto were added in 2022. The decimal column is written out only up to 10⁹ and 10⁻⁹.
FAQ
Is the symbol case-sensitive?+
Yes. M (mega, 10⁶) and m (milli, 10⁻³) are a billion times apart; P (peta) and p (pico) likewise.
Is a kilobyte 1,000 or 1,024 bytes?+
In the SI, kilo always means 1,000. The 1,024 multiple is the binary prefix kibi (Ki).