SI prefixes
| Prefix | Symbol | Factor | Ordinary Notation* | Name | |
|---|---|---|---|---|---|
| yotta | Y | 1024 | 1 000 000 000 000 000 000 000 000 | septillion | |
| zetta | Z | 1021 | 1 000 000 000 000 000 000 000 | sextillion | |
| exa | E | 1018 | 1 000 000 000 000 000 000 | quintillion | |
| peta | P | 1015 | 1 000 000 000 000 000 | quadrillion | |
| tera | T | 1012 | 1 000 000 000 000 | trillion | |
| giga | G | 109 | 1 000 000 000 | billion | |
| mega | M | 106 | 1 000 000 | million | |
| kilo | k | 103 | 1 000 | thousand | |
| hecto | h | 102 | 100 | hundred | |
| deka | da | 101 | 10 | ten | |
| 100 | 1 | one | |||
| deci | d | 10-1 | 0.1 | tenth | |
| centi | c | 10-2 | 0.01 | hundredth | |
| milli | m | 10-3 | 0.001 | thousandth | |
| micro | μ | 10-6 | 0.000 001 | millionth | |
| nano | n | 10-9 | 0.000 000 001 | billionth | |
| pico | p | 10-12 | 0.000 000 000 001 | trillionth | |
| femto | f | 10-15 | 0.000 000 000 000 001 | quadrillionth | |
| atto | a | 10-18 | 0.000 000 000 000 000 001 | quintillionth | |
| zepto | z | 10-21 | 0.000 000 000 000 000 000 001 | sextillionth | |
| yocto | y | 10-24 | 0.000 000 000 000 000 000 000 001 | septillionth |
| * | The “ordinary notation” column uses spaces to separate numbers into groups of three digits. In the US, commas are more often used for this purpose, but spaces have the advantage of avoiding confusion when numbers might be seen by readers who use the comma as the decimal point. |
SI prefix etymologies
| Prefix | Pronunciation | Origin |
|---|---|---|
| yotta | YOTE-uh or YOTT-uh | Latin: “eight” [(103)8] |
| zetta | ZETT-uh | Latin: “seven” [(103)7] |
| exa | EX-uh | Greek: “six” [(103)6] |
| peta | PET-uh | Greek: “five” [(103)5] |
| tera | TAIR-uh | Greek: “monster” |
| giga | JIG-uh or GIG-uh | Greek: “giant” |
| mega | MEG-uh | Greek: “big” |
| kilo | KILL-oh | Greek: “thousand” |
| hecto | HECK-toe | Greek: “hundred” |
| deka | DECK-uh | Greek: “ten” |
| deci | DESS-ih | Latin: “tenth” |
| centi | SENT-ih | Latin: “hundredth |
| milli | MILL-ih | Latin: “thousandth” |
| micro | MIKE-roe | Greek: “small” |
| nano | NAN-oh | Greek: “dwarf” |
| pico | PEEK-oh | Spanish: “tiny bit” |
| femto | FEM-toe | Dano-Norwegian: “fifteen” |
| atto | AT-toe | Dano-Norwegian: “eighteen” |
| zepto | ZEP-toe | Latin: “seven” [(103)-7] |
| yocto | YOCK-toe | Latin: “eight” [(103)-8] |
These tables were provided by David Bernklau, Certified Metrication Specialist (CMS), The first table is an expanded version of Table 2 published in Practical Guide to the International System of Units by Dennis Brownridge.