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 for length
- 1 cm = 10 mm
- 1 m = 100 cm
- 1 km = 1000 m
- You need to decide whether to multiply or divide by the conversion factor
- Ask, does the number of units increase or decrease?
- The number of mm is 10 times bigger than the number of cm so mm = cm × 10
- Ask, does the number of units increase or decrease?
- You can do the conversion in stages
- First convert kilometres into metres then metres into centimetres
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 for mass
- 1 g = 1000 mg
- 1 kg = 1000 g
- 1 tonne = 1000 kg
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 for capacity
- 1 l = 1000 ml
- 1 cl = 10 ml
- You must know the basic conversion between volume and capacity
- 1 ml = 1 cm3
Worked example
Convert
(a)
54 cm to mm,
1 cm = 10 mm
54 cm = (54 × 10) mm = 540 mm
540 mm
(b)
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
(c)
485 g to kg.
1000 g = 1 kg
485 g = (485 ÷ 1000) kg
0.485 kg
