SI Prefixes (Quetta to Quecto)
Every SI prefix from quetta to quecto with its symbol, power of ten and multiplier.
SI prefixes scale a unit by a power of ten so numbers stay readable: a millimeter is a thousandth of a meter and a gigahertz is a thousand million hertz. In 2022 four new prefixes were added at each end (quetta, ronna, ronto and quecto), so the range is now 1030 to 10−30.
The table
24 rows
| Prefix | Symbol | Scientific form | Power of ten | Multiplier |
|---|---|---|---|---|
| quetta | Q | E+30 | 30 | x 1 000 000 000 000 000 019 884 624 838 656 |
| ronna | R | E+27 | 27 | x 1 000 000 000 000 000 013 287 555 072 |
| yotta | Y | E+24 | 24 | x 999 999 999 999 999 983 222 784 |
| zetta | Z | E+21 | 21 | x 1 000 000 000 000 000 000 000 |
| exa | E | E+18 | 18 | x 1 000 000 000 000 000 000 |
| peta | P | E+15 | 15 | x 1 000 000 000 000 000 |
| tera | T | E+12 | 12 | x 1 000 000 000 000 |
| giga | G | E+9 | 9 | x 1 000 000 000 |
| mega | M | E+6 | 6 | x 1 000 000 |
| kilo | k | E+3 | 3 | x 1 000 |
| hecto | h | E+2 | 2 | x 100 |
| deca | da | E+1 | 1 | x 10 |
| deci | d | E-1 | -1 | 1 / 10 |
| centi | c | E-2 | -2 | 1 / 100 |
| milli | m | E-3 | -3 | 1 / 1 000 |
| micro | u (mu) | E-6 | -6 | 1 / 1 000 000 |
| nano | n | E-9 | -9 | 1 / 1 000 000 000 |
| pico | p | E-12 | -12 | 1 / 1 000 000 000 000 |
| femto | f | E-15 | -15 | 1 / 1 000 000 000 000 000 |
| atto | a | E-18 | -18 | 1 / 1 000 000 000 000 000 000 |
| zepto | z | E-21 | -21 | 1 / 1 000 000 000 000 000 000 000 |
| yocto | y | E-24 | -24 | 1 / 999 999 999 999 999 983 222 784 |
| ronto | r | E-27 | -27 | 1 / 1 000 000 000 000 000 013 287 555 072 |
| quecto | q | E-30 | -30 | 1 / 1 000 000 000 000 000 019 884 624 838 656 |
Source and notes: SI Brochure, 9th edition (BIPM); quetta, ronna, ronto and quecto were added in 2022.
How to use this table
- Find the prefix or its symbol.
- Multiply a value with that prefix by the multiplier to get the base unit.
- To change prefix, subtract the powers of ten: from mega (6) to kilo (3) multiply by 103.
Worked example
- 2.2 GHz = 2.2 × 109 Hz = 2 200 000 000 Hz.
- 150 mV = 150 × 10−3 V = 0.15 V.
- 4.7 µF = 4.7 × 10−6 F; in nanofarads that is 4.7 × 10−6 ÷ 10−9 = 4 700 nF.
Notes and cautions
- The symbol for kilo is a lowercase k; for mega an uppercase M; for micro the Greek letter µ (or a plain u when the Greek letter is not available).
- Computing uses binary prefixes for memory: a kibibyte (KiB) is 1 024 bytes, while a kilobyte (kB) is 1 000. Disk makers use the decimal meaning.
- Do not combine prefixes: write nanometer, not millimicrometer. The kilogram is the one SI base unit with a prefix built in.
Related tools and guides
FAQ
What is the prefix for 10^-6?
Micro, symbol µ. For example 1 µm is one millionth of a meter.
What comes after tera?
Peta (1015), exa (1018), zetta (1021), yotta (1024), then ronna (1027) and quetta (1030).
Sources
- BIPM, The International System of Units (SI Brochure), 9th edition; the 2022 prefix additions (27th CGPM, Resolution 3).
- SI Brochure, 9th edition (BIPM); quetta, ronna, ronto and quecto were added in 2022.