Perimeter and area
The perimeter is the total distance all the way around the edge of a shape. The area is the amount of flat space a shape covers.
Key idea
Perimeter = add up all the sides. Rectangle area = length × width. Square area = side × side. Perimeter uses cm; area uses cm² (square centimetre).
Working it out
To find a perimeter, walk around the shape and add every side you pass. To find the area of a rectangle or square, multiply two sides together. Take care to keep the correct unit each time, and count all the sides before you add.
Worked example
A rug is 7 cm long and 3 cm wide (on a plan). Find its perimeter and area.
Perimeter = 2 × (7 + 3) = 2 × 10 = 20 cm. Area = 7 × 3 = 21 cm².
Remember
- Perimeter is a length, so use cm.
- Area is a surface, so use cm².
- For a square, all four sides are equal.