GCSE-readySI units and prefixes
Every quantity in science has a unit. These are the international (SI) units and prefixes, from the official SI Brochure.
The seven SI base units
| Quantity | Unit | Symbol |
|---|---|---|
| time | second | s |
| length | metre | m |
| mass | kilogram | kg |
| electric current | ampere | A |
| thermodynamic temperature | kelvin | K |
| amount of substance | mole | mol |
| luminous intensity | candela | cd |
Derived units you will meet at GCSE
| Quantity | Unit | Symbol | In other units |
|---|---|---|---|
| frequency | hertz | Hz | s⁻¹ |
| force | newton | N | kg m s⁻² |
| pressure | pascal | Pa | N/m² |
| energy, work | joule | J | N m |
| power | watt | W | J/s |
| electric charge | coulomb | C | A s |
| potential difference | volt | V | W/A |
| resistance | ohm | Ω | V/A |
Prefixes
| Prefix | Symbol | Multiplies by |
|---|---|---|
| tera | T | 10¹² |
| giga | G | 10⁹ |
| mega | M | 10⁶ |
| kilo | k | 10³ |
| centi | c | 10⁻² |
| milli | m | 10⁻³ |
| micro | µ | 10⁻⁶ |
| nano | n | 10⁻⁹ |
| pico | p | 10⁻¹² |
Your specification says which prefixes you need. The kilogram is the only base unit with a prefix in its name.
Prefix converter
Practice: prefixes
Convert between prefixes, for example kilometres to metres or milliamps to amps.