Derived units
These are derived from the base units as some meaningful combination. Some have special names whereas others are known by the elements that make them up and their mathematical relationship. Only a select few are listed here.
The unit names are only shown where applicable.
| Symbol | Unit name | What it measures |
|---|---|---|
| m2 |
Area (square metre)
See the list of approved units for others.
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|
| m3 |
Volume (cubic metre)
See the list of approved units for others.
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|
| m/s | Speed or velocity (metre per second) | |
| m/s2 |
Acceleration (metre/(second squared))
Rate of change of speed (can be increasing or decreasing) e.g. if a moving object increases its speed by 1 m/s for every second of time that passes, then it is accelerating at the rate of 1 m/s2
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| kg/m3 | Density (kilogram per cubic metre) | |
| N | newton |
Force.
The force which will accelerate a mass of 1 kg at a rate of 1 m/s2
|
| Pa | pascal |
Pressure = 1 N/m2
See list of approved units for others.
|
| J | joule |
Energy
The energy required to accelerate a mass of 1 kg at a rate of 1 m/s2 over a distance of a metre (= 1 N m) Also tied to electrical units (see below). The kJ is the same as that used in nutrition data.
|
| W | watt |
Power
Rate of expenditure of energy equal to 1 joule/second (J/s)
The familiar unit used with electrical appliances, but note the mechanical origin.
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| °C | Celsius |
Temperature
0 °C = 273.15 K
Based the temperatures at which water freezes (0 °C) and boils (100 °C at normal atmospheric pressure)
The same as used in weather forecasts and oven temperatures, etc.
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| Hz | hertz |
Frequency (same as cycle/second)
The unit used for such things as radio channels, sound (pitch) and computer processors (clock speed where 1 'tick' is a cycle).
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