Key Measures
Learn the units, relationships and conventions used to measure length, mass, capacity, time, money and more.
1 kilometres = 1000 metres
The Rules
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44 unitsLength
Metric length steps up and down in thousands, hundreds and tens.
| 1 kilometre | = 1000 metres | |
|---|---|---|
| 1 metre | = 100 centimetres | |
| 1 metre | = 1000 millimetres | |
| 1 centimetre | = 10 millimetres |
Mass
Weight in the metric system works in thousands.
| 1 tonne | = 1000 kilograms | |
|---|---|---|
| 1 kilogram | = 1000 grams | |
| 1 gram | = 1000 milligrams |
Capacity
Liquid measure, and the litre that links to volume.
| 1 litre | = 1000 millilitres | |
|---|---|---|
| 1 litre | = 1000 cubic centimetres | |
| 1 centilitre | = 10 millilitres |
Time
The one system that does not work in tens.
| 1 minute | = 60 seconds | |
|---|---|---|
| 1 hour | = 60 minutes | |
| 1 day | = 24 hours | |
| 1 week | = 7 days | |
| 1 year | = 365 days | |
| 1 leap year | = every 4 years |
Money
Pounds and pence, and the way amounts are written.
| £1 | = 100 pence | |
|---|---|---|
| 50p | = £0.50 | |
| £2.05 | = two pounds and five pence |
Area
Area units square the length step, so the factors square too.
| 1 cm² | = 100 mm² | |
|---|---|---|
| 1 m² | = 10 000 cm² | |
| 1 hectare | = 10 000 m² | |
| 1 km² | = 100 hectares |
Volume
Volume cubes the length step, so the factors cube too.
| 1 cm³ | = 1000 mm³ | |
|---|---|---|
| 1 m³ | = 1 000 000 cm³ | |
| 1 m³ | = 1000 litres |
Metric and Imperial
These are approximate. Use them for checking an answer is sensible, not for exact work.
| 1 inch | ≈ 2.54 cm | |
|---|---|---|
| 1 foot | ≈ 30 cm | |
| 1 mile | ≈ 1.6 km | |
| 1 kilogram | ≈ 2.2 pounds | |
| 1 stone | ≈ 6.35 kg | |
| 1 litre | ≈ 1.75 pints | |
| 1 gallon | ≈ 4.5 litres |
Temperature
Two scales, and the rule for turning one into the other.
| Water freezes | = 0 °C, 32 °F | |
|---|---|---|
| Water boils | = 100 °C, 212 °F | |
| °C to °F | = × 9 ÷ 5 then + 32 | |
| °F to °C | = − 32 then × 5 ÷ 9 |