# What Does Perimeter Mean?

Welcome to page all about 'What does perimeter mean'?.

We will explain what perimeter is and how you can measure it.

There will also be links to some of our other perimeter pages.

## Perimeter of a Rectangle

### Examples

Example 1 The perimeter of the rectangle above is 7 + 2 + 7 + 2 = 18cm.

However, we could also just work out (7 + 2) x 2, as we are simply adding 7 plus 2 twice.

Example 2 This rectangle is actually a square.

The perimeter is 6 + 6 + 6 + 6 = 24cm.

As all the sides of a square are the same length, we just need to multiply the length of one side by 4 to find the perimeter.

So 6cm x 4 = 24cm.

## Perimeter of a Rectilinear Shape

### Examples

Example 1 To find the perimeter of the shape, we just need to add up the length of each of the sides.

Since all the sides have been given to us, we just need to add them up.

So the perimeter is 8 + 3 + 5 + 1 + 3 + 2 = 22cm.

Example 2 In this particular example, there are two sides missing.

However, if we look at the missing side on the left hand side, we can see that it is a long vertical line which is the same length as the two vertical lines on the right hand side put together.

So this missing side must be equal to 5cm + 3cm = 8cm. If we now look at the other missing side, it is a short horizontal line.

You can see that the length of this line added to the 5cm horizontal line is the same length as the 7cm long horizontal line.

So the length of the other missing side must be 7cm - 5cm = 2cm. Now that we have worked out both missing sides, we can finally find the perimeter of the whole shape.

Adding up the sides gives us: 5cm + 3cm + 2cm + 5cm + 7cm + 8cm = 30cm

So the perimeter of the shape is 30cm.

## Perimeter of a Regular Shapes

### Examples

Example 1
Find the perimeter of this equilateral triangle. This shape is an equilateral (regular) triangle with 3 equal sides.

So the perimeter is the length of one side multiplied by 3.

5cm x 3 = 15cm

So the perimeter is 15cm.

Example 2
Find the perimeter of this regular pentagon. This shape is a regular pentagon with sides length 8cm.

So the perimeter of this shape is 8cm x 5 = 40cm

Example 3:
Find the length of each side of this regular octagon. This shape is a regular octagon and we are told that the perimeter is 24cm.

We have to find the length of one side.

We know that length of a side x 8 = 24cm

So the length of a side must be 24 ÷ 8 = 3cm

So the length of each side is 3cm.

### More Recommended Math Resources

Take a look at some more of our resources similar to these.

### Online Perimeter Practice

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