Converting metric units: what children learn
Year 5 pupils learn to convert between metric units: kilometres and metres, metres and centimetres, centimetres and millimetres, kilograms and grams, and litres and millilitres. Metric units are based on 10, 100 and 1,000, so converting means multiplying or dividing by one of these.
In this game children match measurements to the same amount in another unit, such as 2.5 km to 2,500 m or 0.25 kg to 250 g. The measurements include decimals, so children also practise multiplying and dividing decimals by 10, 100 and 1,000.
This topic covers the Year 5 statutory requirement in the National Curriculum in England (Measurement): pupils should be taught to “convert between different units of metric measure (for example, kilometre and metre; centimetre and metre; centimetre and millimetre; gram and kilogram; litre and millilitre)”. Year 5 pupils are usually aged 9–10.
For families following US standards, the closest Common Core standard is 5.MD.A.1, which is taught in Grade 5.
How to play
Pick a card on the left, then the card on the right that matches it. Each game has 6 pairs. Wrong matches are counted as mistakes, and you get three stars for a game with no mistakes.
Step by step
- Know the key facts. 1 km = 1,000 m, 1 m = 100 cm, 1 cm = 10 mm, 1 kg = 1,000 g and 1 litre = 1,000 ml.
- Big unit to small: multiply. Going from a bigger unit to a smaller one, the number gets bigger. 3 km is 3 × 1,000 = 3,000 m.
- Small unit to big: divide. Going from a smaller unit to a bigger one, the number gets smaller. 750 ml is 750 ÷ 1,000 = 0.75 litres.
- Move the digits. Multiplying by 1,000 moves each digit three places to the left: 1.75 km becomes 1,750 m.
Worked examples
Example 1: Convert 4 m to centimetres.
Working: 1 m = 100 cm, so 4 × 100.
Answer: 400 cm
Example 2: Convert 0.25 kg to grams.
Working: 1 kg = 1,000 g, so 0.25 × 1,000.
Answer: 250 g
Example 3: Convert 65 mm to centimetres.
Working: 10 mm = 1 cm, so 65 ÷ 10.
Answer: 6.5 cm
Common mistakes and how to fix them
- Using 100 for every conversion. Only metres and centimetres use 100. Kilo- means 1,000 and milli- means one thousandth.
- Multiplying when going to a bigger unit. Ask: will there be more or fewer of the new unit? Fewer big units means divide.
- Writing 1.5 kg as 1,050 g. 0.5 kg is half a kilogram, which is 500 g, so 1.5 kg is 1,500 g.
Activities to try at home
- Read food labels and convert: is a 1.5 litre bottle more than 1,200 ml?
- Measure a room in metres and centimetres, then write it in centimetres only.
- Look at road signs and running distances in kilometres and convert them to metres.
Ideas for the classroom
- Make a conversion washing line from mm to km.
- Pupils measure objects in one unit and convert to another.
- Solve recipe problems that use g, kg, ml and litres.
Free printable game and worksheet
The free printable starts with a game sheet, such as a colour-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
Does Year 5 include imperial units?
Yes. Year 5 pupils also learn rough equivalents between metric units and common imperial units such as inches, pounds and pints. This game uses metric units.
Why does the game use commas in 1,000?
Commas separate thousands and make large numbers easier to read, as in most UK textbooks.
Can it be played with a keyboard?
Yes. Tab to a card, press Enter to pick it, then pick its partner.