GCSE-readyMetric units and converting measures
Recipes, sports and building all use measures. Knowing how the metric units link makes converting quick.
The metric units
Mass: 1 000 g = 1 kg, 1 000 kg = 1 tonne.
Capacity: 1 000 ml = 1 litre, 100 cl = 1 litre.
| Measure | Small to large |
|---|---|
| Length | 10 mm = 1 cm, 100 cm = 1 m, 1 000 m = 1 km |
| Mass | 1 000 g = 1 kg, 1 000 kg = 1 tonne |
| Capacity | 1 000 ml = 1 l, 100 cl = 1 l |
Converting
Going to a larger unit gives a smaller number: divide. 450 g = 450 ÷ 1 000 = 0.45 kg.
Change to the same unit before adding or comparing.
Time and money
Time is not decimal: 2.5 hours = 2 hours 30 minutes, not 2 hours 50 minutes.
Money: £3.07 = 307p. A calculator showing 4.5 for pounds means £4.50.
Add 1.2 kg and 750 g. Give your answer in kg.
- Change to grams: 1.2 kg = 1 200 g
- 1 200 + 750 = 1 950 g
- 1 950 ÷ 1 000 = 1.95 kg
Answer: 1.95 kg
To a smaller unit, multiply. To a larger unit, divide. Use the same units before adding. Time works in 60s, not 10s.
- Not “3 hours 40 minutes”. That treats the hour as 100 minutes. An hour has 60 minutes.
Try two quick questions
See if it has sunk in. Answers are marked straight away.
2 more questions
Try each one, then tap to check.
Change 4.7 km into metres.
Show the answer
Answer: 4700 m
1 km = 1000 m, so 4.7 × 1000 = 4 700 m.
Change 750 g into kilograms.
Show the answer
Answer: 0.75 kg
1000 g = 1 kg, so 750 ÷ 1000 = 0.75 kg.
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Checked by the GCSE-ready editorial team, 17 October 2026. Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.