How square metres are worked out
Multiply the length by the width, both in metres. A room 4.5 m long and 3 m wide has an area of 4.5 x 3 = 13.5 m².
If you measured in centimetres, convert first: 450 cm is 4.5 m. The calculator does that for you, so the answer is always in square metres.
Worked example
A room measures 4.5 m by 3 m. The area is 13.5 m² and the perimeter is 15 m.
At 20 per square metre, the flooring costs 13.5 x 20 = 270.
The same room in centimetres is 450 by 300, which is 135,000 cm². That is the same area, shown in the unit you measured in.
Adding an allowance
Flooring and paint are usually bought with a waste allowance. Add 5% for a simple rectangular room and 10% or more where there are alcoves or diagonal laying.
This page gives the exact area. Multiply by 1.05 or 1.10 yourself if your supplier expects an allowance, so the figure you buy from is your own decision.
Inputs for the square meter calculator
Length
One side of the space, measured in the unit you choose below.
Width
The other side, at right angles to the length.
Measurement unit
The unit both measurements are in. Changing it converts the numbers you typed, so the same space is described.
Price per square metre
Optional. Multiplied by the area to give a cost. Leave it at 0 to skip the cost row.
CALCULATOR QUESTIONS
Square meter calculator questions
How do I work out square metres?
Multiply the length by the width in metres. A room 4.5 m by 3 m is 13.5 m².
How do I convert centimetres to square metres?
Multiply the two measurements in centimetres and divide by 10,000. 450 cm by 300 cm is 135,000 cm², or 13.5 m².
Why is the area not just the perimeter times something?
Area and perimeter measure different things. Perimeter is the distance around the edge; area is the surface inside it.
Can I use feet and inches?
Choose feet and enter decimal feet, so 10 feet 6 inches is 10.5. The answer is still given in square metres, with your own unit alongside.