What is perimeter?

The perimeter is the distance around the outside of a 2D shape.

The distance can be measured in units like millimetres, centimetres, metres and kilometres.

To work out the perimeter, add up the lengths of all the sides.

Complete this interactive activity to understand how to calculate the perimeter of 2D shapes, then put your knowledge to the test.

Omi has measured each side of this window.

Let's help her calculate the perimeter.

To calculate the perimeter of a shape, like this window, you can add the length of all the sides together.

100cm + 120cm + 100cm +120cm = 440cm

Or, you can multiply the length and width by 2. You can also think about this as doubling.

100cm × 2 = 200cm

120cm × 2 = 240cm

You then add both answers together.

200cm + 240cm = 440cm

So the perimeter of the window is 440cm.

Example 2

Example 3

Dig deep and test what you've learnt in the Mines of Measurement in the Guardians: Defenders of Mathematica game.

Play the full Guardians: Defenders of Mathematica game.