Units & Conversions

Spec reference: Ratio, proportion and rates of change
Key idea: Convert between metric and imperial units and between compound units.

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Metric units

Quantity	Units
Length	mm, cm, m, km
Mass	mg, g, kg, tonnes
Volume/Capacity	ml, cl, l

Key conversions

$$10\text{ mm}=1\text{ cm}100\text{ cm}=1\text{ m}1000\text{ m}=1\text{ km}$$$$1000\text{ g}=1\text{ kg}1000\text{ kg}=1\text{ tonne}$$$$1000\text{ ml}=1\text{ l}1\text{ ml}=1{\text{ cm}}^3$$

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Imperial units (approximate conversions)

Imperial	Metric
1 inch	2.54 cm
1 foot	30 cm
1 mile	1.6 km
1 pound (lb)	454 g
1 stone	6.35 kg
1 pint	568 ml
1 gallon	4.55 litres

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Area and volume conversions

$$1{\text{ m}}^2=\mathrm{10,000}{\text{ cm}}^{2}1{\text{ m}}^3=\mathrm{1,000,000}{\text{ cm}}^3$$

WARNING

When converting areas, square the conversion factor.
When converting volumes, cube the conversion factor.

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Test Yourself

Question 1 of 5

Convert 3.5 km to metres