Converting between metric and imperial units

Converting between metric and imperial units

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Tutor: Labib


Converting between metric and imperial units

​​In a nutshell

The imperial unit system is not used as frequently as the metric unit system but it is still used for some common measurements. The metric and imperial systems can represent the same measurement in a different way and you must be able to convert between the imperial and metric systems. 

Metric and imperial units

The metric and imperial system use different units. It is useful to know the approximate values of imperial units in the metric system. 


1 inch2.5cm1 \space inch \approx 2.5cm​​

1 foot30cm1\space foot \approx30cm​​

1 mile1.6km1 \space mile \approx 1.6km​​


1 ounce30g1 \space ounce \approx 30g​​

1 pound0.5kg1 \space pound \approx 0.5kg​​

1 stone6.5kg1 \space stone \approx 6.5kg   


1 pint0.5 litres1 \space pint \approx 0.5 \space litres

1 gallon4.5 litres1 \ gallon \approx 4.5 \ litres​​

Note: You do not need to memorise these conversions as they will be stated in the question. 

Example 1

Adam's height is 55​ foot 66​ inches. Use the conversions from the table above to calculate his height in centimetres.  

To convert from feet to centimetres multiply by 3030

5 ×30=150cm5 \ \times 30 = 150cm

To convert from inches to centimetres multiply by

6 ×2.5=15cm6\ \times 2.5 = 15cm

150cm+15cm=165cm150cm + 15cm = 165cm

Therefore, Adam is approximately 165cm\underline{165cm}.

Example 2

How many kilometres are there in 55  miles? Use the conversions from the table above. 

1 mile1.6km 1 \ mile \approx 1.6km

To convert miles to kilometres multiply by 1.61.6.

5×1.6=8km5 \times 1.6 = 8km

Therefore, 5 miles8km\underline{ 5 \ miles \approx 8km}.

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