Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!
Print

Maths

Converting measurements

Page:

  1. 1
  2. 2
  1. Back
  2. Next

Converting between metric and imperial units

Here are some examples of metric and imperial measures of length, mass and capacity:

 

 MetricImperial
Lengthmm, cm, m, kminch, foot, yard, mile
Massmg, g, kgounce (oz), pound (lb), stone
Capacityml, cl, lpint, gallon

You will be expected to know some common conversions between metric and imperial units. Some of these are shown below, but check with your teacher which ones you need to learn.

  • 1 km = 5/8 mile
  • 1 m = 39.37 inches
  • 1 foot = 30.5 cm
  • 1 inch = 2.54 cm
  • 1 kg = 2.2 lb
  • 1 gallon = 4.5 litres
  • 1 litre = 1 3/4 pints
Question

A cup has a circumference of 10 inches. What is it in cm?

toggle answer

Answer

We know that 1 inch = 2.54 cm.

We are converting from inches to cm, so we multiply by 2.54

10 × 2.54 = 25.4 cm.

It is easy to get confused over whether to multiply or divide, so here is a way to check your answers:

After doing the conversion, always think about whether your answer should be bigger or smaller than the original number.

In this question, which involves converting inches into cms, we know that cms are smaller than inches, so you should end up with a bigger number than the one you started with. You therefore need to multiply.

Question

Use this method to say which of the following conversions are definitely incorrect?

  • 61 cm = 1860.5 feet
  • 5 gallons = 22.5 litres
  • 14 lb = 30.8 kg

toggle answer

Answer

Remember cm are smaller than feet, so 61 cm = 1860.5 feet must be wrong.

And pounds are smaller than kg, so 14lb = 30.8 kg must be wrong too.

Page:

  1. 1
  2. 2
  1. Back
  2. Next

Back to Geometry and measures index

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.