Measurement: Converting Units
Measurement: Converting Units is the Year 4 topic covering converting between related metric units of length, mass, capacity and time, understanding that each unit is a fixed multiple, usually 10, 100 or 1000, of the next smaller unit.
Before you start
Make sure you're comfortable with these topics first:
Method
- Learn the key metric facts: 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km, 1000 g = 1 kg, and 1000 ml = 1 litre.
- To convert from a smaller unit to a larger unit (for example cm to m), divide by the conversion number.
- To convert from a larger unit to a smaller unit (for example m to cm), multiply by the conversion number.
- Learn the key time facts too: 60 seconds = 1 minute and 60 minutes = 1 hour, and use the same multiply-or-divide rule to convert between them.
- Before comparing two measurements, convert them to the same unit first so the comparison is fair.
- Check a conversion makes sense: the same measurement written in a smaller unit should always be a bigger number than when it is written in a larger unit.
Worked example
A garden fence is 4 metres 35 centimetres long. Write this length in centimetres only, and then in millimetres only.
- Since 1 m = 100 cm, 4 m = 4 x 100 = 400 cm.
- Add the extra 35 cm: 400 cm + 35 cm = 435 cm, so 4 m 35 cm = 435 cm.
- Since 1 cm = 10 mm, convert 435 cm to mm by multiplying by 10.
- 435 x 10 = 4350 mm, so 4 m 35 cm = 4350 mm.
Practice questions
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Q1Convert 3.2 km into metres.Show answer
Answer: 3200 m (3.2 x 1000)
Q2Convert 750 g into kilograms.Show answer
Answer: 0.75 kg (750 divided by 1000)
Q3A bottle holds 1 litre 250 ml of juice. Write this amount in millilitres only.Show answer
Answer: 1250 ml (1000 ml + 250 ml)
Q4How many minutes are there in 3 hours?Show answer
Answer: 180 minutes (3 x 60)
Q5Ravi's pencil is 145 mm long. Write this length in centimetres.Show answer
Answer: 14.5 cm (145 divided by 10)
Q6Put these three lengths in order from shortest to longest: 2 m, 185 cm, 1900 mm.Show answer
Answer: 185 cm, 1900 mm, 2 m, because in centimetres these are 185 cm, 190 cm and 200 cm
Q7A recipe needs 500 g of flour. Priya has a 2 kg bag of flour. How many grams will be left in the bag after she uses 500 g?Show answer
Answer: 1500 g, because 2 kg = 2000 g and 2000 - 500 = 1500
Q8Explain why 3500 m is the same length as 3.5 km.Show answer
Answer: Because 1000 m = 1 km, 3500 m = 3500 divided by 1000 = 3.5 km; both describe exactly the same distance, just measured in different units.
Exam-style questions
Written in the style of a KS2 Maths exam paper, with a full mark scheme.
A plank of wood is 2 m 8 cm long. A builder cuts off a piece that is 65 cm long. How many centimetres of wood are left? Give your answer in centimetres.
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Circle the measurement that is equal to 4000 ml: 4 litres, 40 litres, 0.4 litres.
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A lorry can carry a maximum load of 5000 kg. It is already carrying 3 crates that each weigh 850 kg. How many more whole kilograms can the lorry carry before it reaches its maximum? Show your working.
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Free printable worksheet
Want more practice on paper? Download the measurement: converting units worksheet pack - 6 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
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