To work out the area of a square or rectangular shape, for example to measure a floor space or a wall, measure both sides from one corner, and then multiply one by the other.

These sides can be referred to as width x height, width x length or base x height.

Let’s look at some examples.

Measuring a floor space

This floor area is a rectangle which measures 3 metres by 6 metres. To calculate the floor area, multiply 3 metres by 6 metres.

3 x 6 = 18, so the floor area is 18 m² (18 square metres).

Measuring wall space

Measure the length and height of each wall, and use these measurements to calculate its area. Then add them together to find the total wall space.

Room measurements:

Height: 2.5 m
Length: 4 m
Width: 3 m

Walls 1 and 3: Length (4) x height (2.5) = 10 m, 2 x 10 = 20

Walls 2 and 4: Length (3) x height (2.5) = 7.5 m, 2 x 7.5 = 15

Total area: 20 + 15 = 35 m² (35 square metres).

You may also wish to subtract, or estimate, the space taken up by windows and doors, for example if working out how much wallpaper or paint to buy.

Try it out

Calculate the number of slabs required to lay paving in a 3 m x 3 m garden area.

Each slab measures 500 x 500 mm.

Toggle solution

You will need 36 slabs.

Each slab is 0.5 x 0.5 = 0.25 m²

The area to be covered is 3 x 3 = 9 m².

Each slab is 0.25 m², so 4 of these will cover 1 m² (0.25 x 4 = 1). Multiply 4 x 9 to find the total required.

Alternatively, 9 ÷ 0.25 = 36.