Metric Conversions
Metric conversion questions require changing between units of length, mass and capacity, such as millimetres, centimetres, metres and kilometres, or grams, kilograms, millilitres and litres, using the standard metric relationships. These conversions underpin later GCSE topics including area, volume, speed and density.
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the key conversion facts: 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km; 1000 g = 1 kg; 1000 ml = 1 litre; 1000 kg = 1 tonne.
- To convert from a smaller unit to a larger unit, divide by the conversion number (e.g. cm to m, divide by 100).
- To convert from a larger unit to a smaller unit, multiply by the conversion number (e.g. kg to g, multiply by 1000).
- When comparing or ordering quantities given in different units, convert them all to the same unit first.
- In worded problems, decide which unit the final answer should be given in, and convert at the end rather than partway through.
- Check your converted answer is a sensible size for the context; a person's height should never come out as 1800 m.
Worked example
A ribbon is 2.4 m long. Priya cuts off 65 cm. Work out the length of ribbon remaining, in centimetres.
- Convert 2.4 m to centimetres: 2.4 x 100 = 240 cm.
- Subtract the length cut off: 240 - 65.
- 240 - 65 = 175.
- Final answer: 175 cm of ribbon remains.
Practice questions
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Exam-style questions
Written in the style of a GCSE Maths exam paper, with a full mark scheme.
A recipe needs 0.85 kg of flour and 650 g of butter. Work out the total mass of flour and butter, in grams.
A plank of wood is 1.8 m long. Tom cuts it into 4 equal pieces. Work out the length of each piece, in centimetres.
A shop sells orange juice in two ways. Bottle A: one bottle containing 1.75 litres of juice. Pack B: a pack of 4 cartons, each containing 450 ml of juice. Priya wants to buy whichever option gives the greater total amount of juice. Work out which option gives the greater amount of juice, and find the difference in millilitres. You must show your working.
See real past-paper questions on metric conversions, organised by topic with official mark schemes →
Free printable worksheet
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