Perimeter or area?
They must not be mixed up:
- The perimeter is the length of the way around the shape. It is measured in cm, m, km… It is the distance you travel going all the way round.
- The area is the measure of the surface, the space the shape takes up. It is measured in cm², m²… It is the number of squares that cover it.
Working out the perimeter
Add up all the sides. For a rectangle of length L and width w, the sides are equal in pairs, so:
Perimeter = (6 + 4) × 2 = 20 cm
Perimeter of a rectangle = (L + w) × 2
For a square, all 4 sides are equal: Perimeter = side × 4. A square with a 5 cm side has a perimeter of 5 × 4 = 20 cm.
Working out the area
For a rectangle, the area is counted in squares: as many rows as the width, as many squares per row as the length. So you multiply:
Area = 6 × 4 = 24 squares = 24 cm²
Area of a rectangle = L × w
For a square: Area = side × side. A square with a 5 cm side has an area of 5 × 5 = 25 cm².
The units (cm and cm²)
This is the key to never mixing them up: the perimeter is a length, written in cm; the area is a surface, written in cm² ("square centimetres").
Worked exercises
Perimeter of a rectangle 8 cm by 3 cm?
Area of a rectangle 8 cm by 3 cm?
Perimeter and area of a square with a 7 cm side?
A rectangle has an area of 20 cm² and a length of 5 cm. What is its width?
Now it's your turn!
On EasyMaths, your child practises perimeter and area with varied shapes and instant marking. The first exercises are free.
Start the exercises →Frequently asked questions
What is the difference between perimeter and area?
The perimeter is the length of the way around a shape (in cm, m…). The area is the measure of its surface, the space it takes up (in cm², m²…).
How do you work out the perimeter of a rectangle?
Add the four sides. Since they are equal in pairs, you calculate (length + width) × 2.
How do you work out the area of a rectangle?
Multiply the length by the width: Area = L × w. The result is given in a square unit, for example cm².