How to calculate square metres
Measure floor area by adding non-overlapping rectangles, or the four walls of one rectangular room by multiplying its perimeter by height. Deduct openings using their total area in the selected square units. Convert centimetres, metres, feet and inches. This is geometric area only, not an estimate of paint, tiles or purchase quantities and not a certified property measurement.
A room 5 × 4 m has 20 m² of floor area. Its walls at a height of 2.5 m total 45 m² before deducting doors and windows.
Results are estimates and depend on the supplied values.
Area calculation guide
Rectangular floor
Multiply length by width using the same length unit.
5 m × 4 m = 20 m².
L-shaped rooms
Break the floor into non-overlapping rectangles and add their areas. Do not count overlaps twice.
5 × 4 m + 2 × 3 m = 26 m² if the rectangles do not overlap.
Wall area
For a rectangular room of constant height, multiply the perimeter by the height, then subtract doors and windows.
2 × (5 + 4) × 2.5 = 45 m²; less 3 m² of openings = 42 m².
Units
1 m = 100 cm = 3.28084 ft. Area conversion squares the length factor.
1 ft² = 0.09290304 m².
Important limitations
Zones must be rectangular and non-overlapping. Arbitrary polygons and sloped surfaces are not supported; room measurement is not a substitute for a professional or legal survey.
Frequently asked questions
How do I find room square metres?
Multiply length by width for a rectangular room. Split L-shaped floors into non-overlapping rectangles and sum.
How do I calculate wall area?
Use wall mode and enter room length, width and height, then subtract door and window areas.
Does this estimate tiles or paint?
It calculates geometric area, not cutting losses, waste, coverage, coats or purchase quantities.
Can I use feet or inches?
Yes. Select the unit before entering dimensions. Results are displayed in square metres.