SI defines 7 base units: s, m, kg, A, K, mol, cd.
There are 22 of derived units with their own symbols defined.
These correspond to the base ones like so:
| Derived unit | Equivalent using base units |
|---|
| rad | 1 |
| sr | 1 |
| Hz | s^-1 |
| N | kg m s^-2 |
| Pa | kg m^-1 s^-2 |
| J | kg m^2 s^-2 |
| Derived unit | Equivalent using base units |
|---|
| W | kg m^2 s^-3 |
| C | A s |
| V | kg m^2 s^-3 A^-1 |
| F | kg^-1 m^-2 s^4 A^2 |
| Ω | kg m^2 s^-3 A^-2 |
| S | kg^-1 m^-2 s^3 A^2 |
| Derived unit | Equivalent using base units |
|---|
| Wb | kg m^2 s^-2 A^-1 |
| T | kg s^-2 A^-1 |
| H | kg m^2 s^-2 A^-2 |
| °C | K |
| lm | cd |
| lx | cd m^-2 |
| Derived unit | Equivalent using base units |
|---|
| Bq | s^-1 |
| Gy | m^2 s^-2 |
| Sv | m^2 s^-2 |
| kat | mol s^-1 |
SI further defines 24 prefixes denoting exponents of 10:
| Symbol | Quantity |
|---|
| Q | 10^30 |
| R | 10^27 |
| Y | 10^24 |
| Z | 10^21 |
| E | 10^18 |
| P | 10^15 |
| Symbol | Quantity |
|---|
| T | 10^12 |
| G | 10^9 |
| M | 10^6 |
| k | 10^3 |
| h | 10^2 |
| da | 10 |
| Symbol | Quantity |
|---|
| d | 10^-1 |
| c | 10^-2 |
| m | 10^-3 |
| μ | 10^-6 |
| n | 10^-9 |
| p | 10^-12 |
| Symbol | Quantity |
|---|
| f | 10^-15 |
| a | 10^-18 |
| z | 10^-21 |
| y | 10^-24 |
| r | 10^-27 |
| q | 10^-30 |
Each input comprises of a (optional) prefix and one of the base or derived
units symbol, except that symbols for decimal multiples and sub-multiples
of "kg" are formed by attaching prefixes to the unit symbol "g". For
example, "10^−6 kg" is written as "mg", not as "µkg". Each such input
should be convert to product of a power of 10 and a product of base units,
as described in the tables above. If the unit is "1", only the power of
ten should be printed. Furthermore, "10^1" should be printed as "10" and
"10^0" as "1". For example, "MJ" should be converted to "10^6 kg m^2 s^-2".