Common Measurement Units
An overview of the units you meet most often, what they measure and how they relate.
The seven SI base units
| Quantity | Unit | Symbol |
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| Length | meter | m |
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| Mass | kilogram | kg |
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| Time | second | s |
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| Electric current | ampere | A |
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| Temperature | kelvin | K |
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| Amount of substance | mole | mol |
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| Luminous intensity | candela | cd |
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Since 2019, all seven are defined by fixed values of physical constants, such as the speed of light and the Planck constant.
Everyday units
| Quantity | Metric | US customary |
|---|
| Length | mm, cm, m, km | inch, foot, yard, mile |
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| Mass / weight | g, kg, tonne | ounce, pound, ton |
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| Volume | mL, L, m³ | teaspoon, cup, pint, quart, gallon |
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| Area | cm², m², hectare, km² | square foot, acre, square mile |
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| Speed | km/h, m/s | mph |
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| Temperature | °C | °F |
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Derived units you will see
| Unit | Measures | Everyday example |
|---|
| watt (W) | power | a 60 W light bulb |
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| kilowatt-hour (kWh) | energy | electricity bills |
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| joule (J), calorie | energy | food labels use kilocalories or kJ |
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| pascal (Pa) | pressure | weather in hPa; tyre pressure in kPa or psi |
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| newton (N) | force | engineering loads |
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| hertz (Hz) | frequency | radio stations, CPU speeds |
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