Choosing metric units for volume and capacity
21 October 2026
Why metric units matter
Choosing the correct metric unit helps your child answer 11+ maths questions accurately. Volume and capacity questions often require them to select the most sensible unit, such as litres or millilitres.
Common metric units for volume and capacity
The main metric units for volume and capacity are millilitres (mL), litres (L) and cubic centimetres (cm³). Millilitres are best for small amounts, litres for larger containers, and cubic centimetres for measuring the volume of solids.
Key insight: Choosing the right unit
Encourage your child to think about the size of the object or amount. For example, a cup of water is measured in millilitres, while a bath holds several litres. Using the correct unit keeps answers clear and makes comparisons easier.
Worked example
A carton of juice contains 2000 millilitres of juice.
First, consider whether millilitres or litres make the answer easier to read.
Since 2000 millilitres is a large number, it can be converted to litres.
There are 1000 millilitres in 1 litre, so 2000 ÷ 1000 = 2 litres.
The correct answer is 2 litres.
Practical tips for parents
Encourage your child to estimate before answering. If the number is very large or very small, another unit might be more suitable. Practise with real-life objects like bottles or measuring jugs to make the concept clear.
