Converting Units
How do I convert between units for lengths?
- For metric units, conversion can be done by simply multiplying or dividing by powers of 10
- You need to know the basic conversions
- 1 cm = 10 mm
- 1 m = 100 cm
- 1 km = 1000 m
- To decide whether to multiply or divide you need to ask yourselves does the number of units increase or decrease
- e.g. The number of mm is 10 times bigger than the number of cm so mm = cm × 10
- You can do the conversion in stages
- First convert kilometres into metres then metres into centimetres
- If you are given an imperial conversion (such as miles to kilometres) then you can use ratios to help with the conversions
- There are 5 miles in 8 kilometres so to find how many miles are in 13 kilometres you would solve
How do I convert units for mass?
- For metric units, conversion can be done by simply multiplying or dividing by powers of 10
- You need to know the basic conversions
- 1 g = 1000 mg
- 1 kg = 1000 g
- 1 tonne = 1000 kg
- If you are given an imperial conversion (such as pounds to kilograms) then you can use ratios to help with the conversions
- e.g. There are 2.2 pounds in 1 kilogram so to find how many kilograms are in 10 pounds you would solve
How do I convert units for volume/capacity?
- For metric units, conversion can be done by simply multiplying or dividing by powers of 10
- You need to know the basic conversions
- 1 l = 1000 ml
- 1 cl = 10 ml
- 1 ml = 1 cm3
- If you are given an imperial conversion (such as pints to litres) then you can use ratios to help with the conversions
- e.g. There are 1.75 pints in 1 litre so to find how many litres are in 5 pints you would solve
Worked example
Convert
54 cm to mm,
1 cm = 10 mm
54 cm = (54 × 10) mm = 540 mm
540 mm
12 300 cm to km,
First convert from cm to m.
100 cm = 1 m
12 300 cm = (12 300 ÷ 100) m = 123 m
Now convert from m to km.
1000 m = 1 km
123 m = (123 ÷ 1000) km = 0.123 km
0.123 km
485 g to kg.
1000 g = 1 kg
450 g = (450 ÷ 1000) kg
0.45 kg