Metric SI Prefixes Chart
SI prefixes express very large or very small values as powers of ten. In 2022 the CGPM added
ronna (1027), quetta (1030), ronto (10−27),
and quecto (10−30).
Largest & smallest: Quetta (Q) = 1030; Quecto (q) = 10−30.
Complete SI prefix list — quecto (10⁻30) → quetta (10³⁰)
| SI Prefixes |
| Factor |
Name |
Symbol |
Example (metre) |
| 1030 | quetta | Q | 1 Qm = 1030 m |
| 1027 | ronna | R | 1 Rm = 1027 m |
| 1024 | yotta | Y | 1 Ym = 1024 m |
| 1021 | zetta | Z | 1 Zm = 1021 m |
| 1018 | exa | E | 1 Em = 1018 m |
| 1015 | peta | P | 1 Pm = 1015 m |
| 1012 | tera | T | 1 Tm = 1012 m |
| 109 | giga | G | 1 Gm = 109 m |
| 106 | mega | M | 1 Mm = 106 m |
| 103 | kilo | k | 1 km = 103 m |
| 102 | hecto | h | 1 hm = 102 m |
| 101 | deca | da | 1 dam = 10 m |
| 10−1 | deci | d | 1 dm = 10−1 m |
| 10−2 | centi | c | 1 cm = 10−2 m |
| 10−3 | milli | m | 1 mm = 10−3 m |
| 10−6 | micro | µ | 1 µm = 10−6 m |
| 10−9 | nano | n | 1 nm = 10−9 m |
| 10−12 | pico | p | 1 pm = 10−12 m |
| 10−15 | femto | f | 1 fm = 10−15 m |
| 10−18 | atto | a | 1 am = 10−18 m |
| 10−21 | zepto | z | 1 zm = 10−21 m |
| 10−24 | yocto | y | 1 ym = 10−24 m |
| 10−27 | ronto | r | 1 rm = 10−27 m |
| 10−30 | quecto | q | 1 qm = 10−30 m |
Writing Rules (Quick)
- Prefix symbols are case-sensitive:
k (kilo), M (mega), G (giga), µ (micro).
- Use the micro symbol µ; if unavailable,
u is a temporary substitute. Standards and publications use µ.
- Leave a space between number and unit:
25 °C, 10 kN.
- Binary prefixes (KiB, MiB, …) are powers of 2; SI prefixes are powers of 10.
Example
A prefix attaches directly to the unit symbol and behaves algebraically:
1 cm³ = (10⁻² m)³ = 10⁻⁶ m³
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Supplements
References
- BIPM — The International System of Units (SI) & SI Prefixes (CGPM 2022 resolution).
- NIST — Metric (SI) Prefixes overview.