si_prefixes
Table of Contents
SI prefixes
| Stan Zurek, SI prefixes, Encyclopedia Magnetica, https://www.e-magnetica.pl/doku.php/si_prefixes |
SI prefixes - a system of decimal multipliers, defining multiples and sub-multiples of SI units.1)
An SI prefix is added before the given SI unit, so that very large, and very small values can expressed in a concise form. There should be a space between the number and the SI unit, but not between the prefix and and unit.2)
| Name | Symbol | Multiplying factor | |
|---|---|---|---|
| yotta | Y | 1024 | 1 000 000 000 000 000 000 000 000 |
| zetta | Z | 1021 | 1 000 000 000 000 000 000 000 |
| exa | E | 1018 | 1 000 000 000 000 000 000 |
| peta | P | 1015 | 1 000 000 000 000 000 |
| tera | T | 1012 | 1 000 000 000 000 |
| 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 |
| (none) | (none) | 1 | 1 |
| deci | d | 10–1 | 0.1 |
| centi | c | 10–2 | 0.01 |
| milli | m | 10–3 | 0.001 |
| micro | µ | 10–6 | 0.000 001 |
| nano | n | 10–9 | 0.000 000 001 |
| pico | p | 10–12 | 0.000 000 000 001 |
| femto | f | 10–15 | 0.000 000 000 000 001 |
| atto | a | 10–18 | 0.000 000 000 000 000 001 |
| zepto | z | 10–21 | 0.000 000 000 000 000 000 001 |
| yocto | y | 10–24 | 0.000 000 000 000 000 000 000 001 |
| * The exception is the unit of kilogram (kg), which should not be used with an additional prefix.3) * If Greek letters are not available (especially in older publications or software), the symbol micro “µ” is typically replaced by “u”.4) |
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Examples
A few examples in the table below illustrate the correct usage.
| Full SI unit name | SI unit symbol | first example | second example |
|---|---|---|---|
| 0.0012 second | 0.0012 s | 1.2 ms | 1200 μs |
| 9.8765 × 1011 ohm | 9.8765 × 1011 Ω | 987.65 GΩ | 0.98765 TΩ |
| 1234 hertz | 1234 Hz | 1.234 kHz | 0.001234 MHz |
| 0.0000002 metre | 0.0000002 m | 0.2 μm | 200 nm |
The prefixes can be also added to the full names of units, forming one word, for example: millimetre, nanotesla, gigaohm, microsecond, which are then to be treated as a single word.5)
See also
References
1)
The International System of Units (SI): Prefixes, {accessed 2021-05-01}
2),
3),
5)
Bureau International des Poids et Mesures, The International System of Units (SI), 9th edition, 2019, {accessed 2021-04-10}
4)
LT wiki, Email interview with PSpice founder Paul Tuinenga, {access 2021-05-03}
si_prefixes.txt · Last modified: 2023/09/05 14:36 by stan_zurek