SI Metric Prefixes Reference
The International System of Units (SI) defines a set of prefixes that indicate powers of ten. These prefixes are attached to SI base units to form multiples and submultiples (e.g., kilo + metre = kilometre = 1,000 metres). In 2022, the BIPM added four new prefixes: ronna, quetta, ronto, and quecto.
Source: BIPM (Bureau International des Poids et Mesures) - the international body for the SI. All SI definitions are public domain.
| Prefix | Symbol | Power of 10 | Value |
|---|---|---|---|
| quetta | Q | 10^30 | 1,000,000,000,000,000,000,000,000,000,000 |
| ronna | R | 10^27 | 1,000,000,000,000,000,000,000,000,000 |
| yotta | Y | 10^24 | 1,000,000,000,000,000,000,000,000 |
| zetta | Z | 10^21 | 1,000,000,000,000,000,000,000 |
| exa | E | 10^18 | 1,000,000,000,000,000,000 |
| peta | P | 10^15 | 1,000,000,000,000,000 |
| tera | T | 10^12 | 1,000,000,000,000 |
| giga | G | 10^9 | 1,000,000,000 |
| mega | M | 10^6 | 1,000,000 |
| kilo | k | 10^3 | 1,000 |
| hecto | h | 10^2 | 100 |
| deca | da | 10^1 | 10 |
| (base) | 10^0 | 1 | |
| 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 | 0.000000000001 |
| femto | f | 10^-15 | 0.000000000000001 |
| atto | a | 10^-18 | 0.000000000000000001 |
| zepto | z | 10^-21 | 10^-21 |
| yocto | y | 10^-24 | 10^-24 |
| ronto | r | 10^-27 | 10^-27 |
| quecto | q | 10^-30 | 10^-30 |
A metric prefix is a modifier word placed before a unit name that indicates a specific power of ten. For example, "kilo" (k) means 1,000, so a "kilogram" is 1,000 grams. "Milli" (m) means 0.001, so a "millimetre" is 0.001 metres.
Kilo (k) = 10^3 = 1,000. Mega (M) = 10^6 = 1,000,000 (one million). So 1 megabyte = 1,000 kilobytes (in SI, base-10). Note: in computing, "kilo" sometimes means 1,024 (2^10), and "mega" 1,048,576 (2^20) - the IEC introduced kibibyte (KiB) and mebibyte (MiB) to distinguish these.
In 2022, the BIPM added four new prefixes: ronna (R, 10^27), quetta (Q, 10^30), ronto (r, 10^-27), and quecto (q, 10^-30). These were needed as data volumes and scientific measurements approach the ronnabyte and quettabyte range.
For the most part, yes. The standard prefixes go by powers of 1,000 (kilo, mega, giga, tera, etc.). However, there are also hecto (10^2), deca (10^1), deci (10^-1), and centi (10^-2) for everyday convenience - these are multiples of 10 or 100.