Length is a measurement that identifies the distance between two points. It also measures an object’s length, height, and width.

Children will learn about length in maths lessons to help them solve practical problems in learning and life.

As part of the learning material, pupils will need to learn the different units of length measurement. So let’s look into this a bit further.

The Metric System: Units of Measurement of Length

Based on the metric system, the standard unit of length is a meter (m). But sometimes, the meter might not be suitable for measuring – for example; our fingers are much shorter than a meter! So that’s why there are other units we can convert a meter into to make it easier for us.

Here are some of the most common units of measuring length:

Millimeter (mm)

A millimeter is a tiny unit of length equal to 0.001 meters. Children can put 10-15 pieces of paper on each other to see how small a millimeter is!

Centimeter (cm)

The following unit of measuring length is a centimeter (cm). One centimeter is equivalent to 10 mm, so it’s a larger unit than millimeters. However, it’s equal to 0.01 meters, making it a relatively small unit. On average, mobile phones today are about 11-13 centimeters.

Meters (m)

When we have 100 centimeters, this makes 1 meter. This is the standard unit of length and is very often used daily. For instance, during the Covid-19 pandemic, we were told to keep a 2-meter distance.

Kilometer (km)

A kilometer is a large unit of measurement of length. It’s equal to 1000 meters. It’s often used when measuring the distance between cities and countries.

The Metric System: Converting between the Different Units

Here’s a handy reference guide on converting between the different units of measurement of length:

  1. Millimetres to other units
  • 1 millimetre = 0.1 centimetre
  • 1 millimetre = 0.001 metre
  • 1 millimetre =0.000001 kilometre
  1. Centimetres to other units
  • 1 centimetre = 10 millimetres
  • 1 centimetre = 0.01 metre
  • 1 centimetre = 0.00001 kilometre
  1. Kilometres to other units
  • 1 kilometre = 1000000 millimetres
  • 1 kilometre = 100000 centimetres
  • 1 kilometre = 1000 metres

Imperial Units of Measurement of Length

The imperial unit system, also known as the British Imperial, is a system of measuring length, which uses different units of measurement than the ones explained above. Here are a few of the common imperial units which are used today:

Inch (in)

An inch is about two and a half centimeters. For example, most pencils are 5 inches long.

Foot (ft)

A foot (not the body part!) is 12 inches or around 30.48 centimeters.

Yard (yd)

One yard equals 3 ft, and it’s a little less than a meter (precisely 0.9144).

Mile (mi)

A mile is equal to 1.6 kilometers. This unit is often used to measure distances in the United Kingdom. For example, if you travel from Manchester to Birmingham, the distance is 85 miles.

The Imperial Unit System: Converting between the Different Units

Here are the most common measures that pupils will need to learn to convert:

  • 1 inch = 2.5 centimetres
  • 1 foot = 12 inches
  • 1 foot = 30.48 centimetres
  • 1 yard = 3 feet
  • 1 yard = 0.91 metres
  • 1 mile = 1.6 kilometres
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