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Measuring length

Length is a measure of how long or wide something is. Rulers and tape measures can be used to measure length.

A ruler

Metric measurements

Length is measured in millimetres (mm), centimetres (cm), metres (m) or kilometres (km). These are known as metric units of length.
1 cm = 10 mm
1 m = 100 cm
1 km = 1000 m

Remember the following to help you estimate lengths:

  • 1 cm is about the width of a staple.

  • 1 m is about the width of a single bed.

Imperial measurements

Miles, feet and inches are old units of length. These are known as imperial units of length but are not now commonly used in maths.
There are 12 inches in a foot.
An inch is roughly equal to 2.5 centimetres.
A foot is roughly equal to 30 centimetres.
A mile is roughly equal to 1.5 kilometres.

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