Metric Conversions for KS2 SATs
Converting between metric units is one of those topics that sounds simple but catches out loads of children in the SATs. The good news? There are only a handful of conversions your child actually needs to know, and they all follow the same “multiply or divide by 10, 100 or 1000” pattern.
The Key Conversions
Your child needs to know these cold:
Length: 10 mm = 1 cm | 100 cm = 1 m | 1000 m = 1 km
Mass: 1000 g = 1 kg
Capacity: 1000 ml = 1 litre
That’s it. Five conversions. Every measurement question in the SATs uses one of these. If your child can recall them instantly, they’re halfway to the marks already.
Converting to Smaller Units (Multiply)
Going from a bigger unit to a smaller one means you’ll have more of them. So you multiply.
3.5 km → metres
3.5 × 1000 = 3500 m
2.4 kg → grams
2.4 × 1000 = 2400 g
Think of it this way: one kilometre is a long way, so there must be lots of metres in it. More of a smaller unit — multiply.
Converting to Larger Units (Divide)
Going from a smaller unit to a bigger one means you’ll have fewer of them. So you divide.
4500 ml → litres
4500 ÷ 1000 = 4.5 litres
350 cm → metres
350 ÷ 100 = 3.5 m
SATs-Style Word Problems
Step 1: Convert 1.5 litres to ml → 1.5 × 1000 = 1500 ml
Step 2: 1500 − 350 = 1150 ml
Answer: 1150 ml
The key step is converting both amounts to the same unit before calculating. The question tells you which unit to use for your answer — always check.
Common Mistakes to Watch For
- Multiplying when they should divide (or vice versa) — ask your child: “Am I going to have more or fewer?” More → multiply. Fewer → divide.
- Using the wrong conversion factor — mixing up ×100 with ×1000. Metres to centimetres is ×100, not ×1000.
- Forgetting to convert before calculating — you can’t subtract millilitres from litres directly. Same unit first.
- Giving the answer in the wrong unit — the question asks for metres but your child gives centimetres. Read the question twice.
Related Topics
Put it into practice
Free, self-marking questions on this topic — no sign-up needed.
Ready to practise?
Build confidence with SATs-style questions
Start free →