Units and converting measures
Metric units, imperial units, scales and speed
We measure length, mass and capacity in different units. Converting between them is all about multiplying or dividing by the right number.
Metric conversions
| Length | Mass | Capacity |
|---|---|---|
| 10 mm = 1 cm | 1,000 g = 1 kg | 1,000 ml = 1 litre |
| 100 cm = 1 m | 1,000 kg = 1 tonne | 100 cl = 1 litre |
| 1,000 m = 1 km |
Big unit → small unit: multiply. Small unit → big unit: divide.
Useful approximations: 5 miles ≈ 8 km, 1 kg ≈ 2.2 pounds (lb), 1 inch ≈ 2.5 cm.
Speed = distance ÷ time.
Worked examples
Example 1. Convert 3.6 m to cm.
Example 2. Convert 2,450 g to kg.
Example 3. Roughly how many km is 25 miles?
Example 4. A car travels 150 km in 2 hours. What is its average speed?
Top tips and common mistakes
- Check your answer makes sense: there should be more of a smaller unit.
- Make sure all measurements are in the same unit before you add them.
- Read scales carefully: work out what each small division is worth.
I used conversions when we baked with an old recipe in ounces. Maths in the kitchen!
Practise
Answer as many as you like. Every question is new, and you get a “correct” tick for each one you get right first time. Use “Show answer” to see a worked solution.
Quiz: earn your stamp
Printable worksheet
Units and converting measures worksheet. The questions come first and the answers for grown-ups are on the last page, so you can print just the question pages.
Printing is optional. A4 size.