Prior to the Metric system of measurement being formally adopted, the Imperial system was used in the UK and is still in use in every day life. Many people still think in 'pounds and ounces', for example when following a recipe. Distances in the UK are also given in 'miles', and speeds in 'miles per hour'.

Unlike the decimal based Metric system, Imperial measures are made up of varying quantities of smaller measures. For example, there are 12 ounces in a pound (1 lb), and 14 lb in a stone.

Some conversions between Imperial and Metric measures are easier to estimate than others, for example 1 mile is approximately 1.6 kilometres, and 1 inch is approximately 2.5 centimetres.

Approximate (rounded down) conversion rates for common length, weight and volume measures are summarised below.

Length

The imperial system of measuring length includes inches, feet and miles.

1 cm = 0.3937 inches (in)
1 m = 3.2808 feet (ft)
1 km = 0.6214 miles (mi)

1 inch (in) = 2.54 cm
1 foot (ft) = 30.48 cm, 0.3048 m
1 mile = 1.6093 km

Weight

The imperial system of measuring weight, or mass, includes ounces, pounds and stones.

1 g = 0.0353 ounces (oz)
1 kg = 2.2046 pounds (lb)

1 ounce (oz) = 28.3495 g
1 pound (lb) = 0.4536 kg
1 stone = 6.3503 kg

Volume

The Imperial system of measuring volume includes pints and gallons.

1 litre  = 1.7597 pints

1 pint = 0.5683 litres
1 gallon = 4.5461 litres

Try it out

What is 12.5 stone to the nearest kilogram?

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