Units and conversion graphs

To change to a smaller unit, multiply (there are more of them). To change to a bigger unit, divide.

Example: change 3.4 km to metres, 2500 g to kilograms, and 750 ml to litres.

1. km to m: smaller unit, so × 1000: 3400 m
2. g to kg: bigger unit, so ÷ 1000: 2.5 kg
3. ml to litres: bigger unit, so ÷ 1000: 0.75 litres

Area units are squared, so you square the conversion factor. Volume units are cubed, so you cube it.

• 1 m = 100 cm, so 1 m² = 100 × 100 = 10 000 cm²
• 1 m³ = 100 × 100 × 100 = 1 000 000 cm³
• 1 cm³ = 1 ml, so 1000 cm³ = 1 litre

Example: change 3.5 m² to cm², and 2 400 000 cm³ to m³.

1. 3.5 × 10 000 = 35 000 cm²
2. 2 400 000 ÷ 1 000 000 = 2.4 m³

Imperial units, such as miles, pounds and pints, are still used in the UK. A question will give you the conversion you need, such as:

1. Find how many times the given amount fits into the amount you have.
2. Multiply the other side of the conversion by the same number.

Example: 5 miles ≈ 8 km. Change 40 miles to kilometres.

1. 40 ÷ 5 = 8, so 40 miles is 8 lots of 5 miles
2. 8 × 8 = 64 km

A conversion graph is a straight line through the origin. Read across from one axis to the line, then down (or across) to the other.

Example: use the graph to change 30 miles to kilometres, and 200 km to miles.

1. Up from 30 miles to the line, then across: 48 km
2. 200 km is off the graph. 200 km = 2.5 × 80 km, and 80 km = 50 miles
3. 2.5 × 50 = 125 miles

For a value off the graph, convert a value you can read, then multiply.