11+ Maths: Choosing Metric Units (Volume & Capacity)
26 October 2026
Choosing metric units for volume and capacity
Understanding metric units for volume and capacity is an important skill for the 11+ Maths exam. Children need to know when to use litres (l) and millilitres (ml), and how to convert between them.
Key insight: Encourage your child to check that all measurements are in the same unit before starting a calculation. This helps avoid common mistakes when comparing or adding volumes.
Worked example
Step 1: Problem
A bottle holds 1.5 litres of juice. It is filled with 750 millilitres of water. How full is the bottle?
Step 2: Compare units
The bottle's capacity is in litres, but the amount filled is in millilitres. Convert one so both are the same. 1 litre = 1000 millilitres.
Step 3: Convert units
1.5 litres = 1500 millilitres.
Step 4: Calculate
750 millilitres ÷ 1500 millilitres = 0.5. The bottle is half full.
Supporting your child
Practise recognising when to use litres for larger amounts (like a bucket or drinks bottle) and millilitres for smaller quantities (like a medicine spoon). Use real-life containers at home to help your child visualise different capacities.
Quick practice ideas
Ask your child to estimate and then measure the capacity of different containers in the kitchen. Challenge them to convert between litres and millilitres, and to explain which unit makes sense for each object.
