Square metre calculator: in short
Multiply the length by the width of a room in metres to get its square metres (m²), then add the rooms up. A room of 4.2 m by 3.5 m is 14.7 m². A room that is not a rectangle: split it into rectangles first and add the parts.
How to calculate square metres
- Measure the length and the width of the room in metres, wall to wall, at floor level.
- Multiply them: length × width = square metres. 4.2 × 3.5 = 14.7 m².
- Do the same for every room, then add the rooms for the total.
- Round only the total, not every room on the way.
Centimetres, millimetres and feet
Change every size to metres before you multiply: 420 cm is 4.2 m, and 3,500 mm is 3.5 m. Do not mix a size in metres with one in centimetres.
In feet? The calculator takes 13′ 9″ as well and gives both numbers. One square metre is 10.76 square feet (a foot is exactly 0.3048 m).
Example: a two-bedroom flat
The total is the floor area of the rooms, measured inside the walls. The walls between the rooms are not in it.
| Room | Size | Square metres | Square feet |
|---|---|---|---|
| Living room | 5.2 × 4.1 m | 21.32 m² | 229 sq ft |
| Kitchen | 3.4 × 2.6 m | 8.84 m² | 95 sq ft |
| Bedroom 1 | 4 × 3.5 m | 14 m² | 151 sq ft |
| Bedroom 2 | 3.2 × 2.8 m | 8.96 m² | 96 sq ft |
| Bathroom | 2.4 × 1.9 m | 4.56 m² | 49 sq ft |
| Hall | 4.5 × 1.2 m | 5.4 m² | 58 sq ft |
| Total | 63.08 m² |
L-shaped rooms and bay windows
Split an L-shaped room into two rectangles and add them. A room of 5 × 4 m with a corner of 2 × 1.5 m cut out is 20 m² minus 3 m², so 17 m². A bay window is a rectangle or a trapezoid of its own.
Square metre or square meter?
The same unit. "Metre" is the spelling in the UK, Ireland, Australia, New Zealand and Canada; "meter" is the American spelling. The symbol is m² everywhere.
The square metres of a whole home
Add every room on each floor. Keep a garage, a shed, a balcony and a loft you cannot stand in on their own lines: an estate agent or a valuer usually lists them apart. Measuring codes differ per country; when a number has to match a listing or a valuation, check which code they use.
To draw the rooms and get the total per floor at once, use the floor plan editor: it keeps floors, outdoor space and low parts apart and exports a plan with the square metres.
Figure 1. One floor of 7.5 × 5 m. The rooms add up to 37.5 m².
Sources
- U.S. Survey Foot: from 2023 only the international foot (0.3048 m), National Institute of Standards and Technology · Checked against the source on October 2, 2026
About this page · Written by the Squaremetry team, based on U.S. Survey Foot: from 2023 only the international foot (0.3048 m). Last checked on October 5, 2026. Found a mistake? Send us a message.