# Converting units

**Converting units**

Converting between units can be done using the following methods:

- Using a formula
- When comparing measurements

When comparing weights, they are converted to the same unit. The unit used are normally **metric units**.

**Metric units**

Metric unit of system is based on powers of ten and uses the following prefixes:

- Kilo – one thousand
- Centi – one hundredth
- Milli – on thousandth
- Micro – one millionth

Base units are then used with the metric system:

- metre – measures length
- grem – measures mass
- litre – measures capacity

**Metric units of length, mass and capacity**

The following metric conversions are used for length, mass and capacity (liquid volume):

Length – 1 km (1,000 m), 1 m (100 cm), 1 m (1,000 mm), 1 cm (10 mm)

Mass – 1 tonne (1,000 kg), 1 kg (1,000 g), 1 g (1,000 mg)

Capacity & Volume – 1 litre (1000 ml), 1 cl (10 ml), 1 m² (1000 litres), 1 cm³ (1 ml)

Point to note: 1 hectare (100 m x 100 m or 10, 000 m²)

**Metric units of area and volume**

Metric units for area are: mm², cm², m², km²

e.g. 1 m² = 100 cm x 100 cm, 1 cm² = 10 mm x 10 mm

Metric units for volume are: mm³, cm³, m³, km³

e.g. 1 m³ = 100 cm x 100 cm x 100 cm = 1,000,000 cm³

**Converting metric units**

To convert using metric units, the following rules are applied:

- To covert from a large metric unit to a smaller unit,
**multiply**by 10, 100 or 1000 - To covert from a smaller metric unit to a larger unit,
**divide**by 10, 100 or 1000

For example:

Convert 0.45 kg to grams: 0.45 kg x 1000 g = 450 g

Convert 7.8 cm to metres: 7.8 cm ÷ 100 m = 0.078 m

**Imperial units**

Imperial units use the following conversions:

1 foot = 12 inches

1 yard = 3 feet

1 pound = 16 ounces

1 stone = 14 pounds

1 gallon = 8 pints

**Converting imperial to metrics units**

Imperial units are converted to metric as follows:

5 miles = 8 kilometres

1 foot = 30 centimetres

1 inch = 2.5 centimetres

1 kilogram = 2.2 pounds

1 gallon = 4.5 litres

1 litre = 1.75 pints