Choosing and converting metric units for 11+ maths
21 October 2026
Why metric units matter in 11+ maths
Choosing the correct metric unit is a key skill for the 11+ exam. Children need to know whether to use millimetres, centimetres, metres or kilometres for length, and similar choices for mass and capacity. This helps them answer real-world questions confidently.
How to choose the right unit
Encourage your child to think about the size of the object or amount. For example, a pencil is best measured in centimetres, while the distance between cities is measured in kilometres. Picking the right unit makes answers more accurate and realistic.
Converting metric units step by step
To convert between metric units, use multiplication or division by 10, 100 or 1000. This works because the metric system is based on powers of ten. Remind your child to check whether they are converting to a larger or smaller unit.
Worked example
Imagine you have 2500 millilitres of water and want to know how many litres that is.
First, remember that 1000 millilitres make 1 litre.
Divide 2500 by 1000 to convert millilitres to litres.
2500 ÷ 1000 = 2.5
The correct answer is 2.5 litres.
Why practice is important
Regular practice with choosing and converting metric units builds confidence. It helps children avoid common mistakes and prepares them for more complex 11+ questions.
Key insight: Practising both choosing the right metric unit and converting between units gives children a strong foundation in measurement, which is vital for 11+ maths success.
