How to calculate square metres
- 1.
Pick a shape
Rectangle, several rooms, L-shape, triangle, circle or trapezoid.
- 2.
Choose the unit
Enter dimensions in metres or centimetres - the result is always in m².
- 3.
Enter dimensions
For several rooms, add each one separately and the calculator adds them up.
- 4.
Read the result
See m², ares and hectares, and the total cost if you enter a price per m².
Area formulas
| Shape | Formula | Example |
|---|---|---|
| Rectangle | a × b | 5 × 4 m = 20 m² |
| L-shape | A × B − C × D | 8 × 6 − 3 × 2 = 42 m² |
| Triangle | base × height / 2 | 10 × 6 / 2 = 30 m² |
| Triangle from sides (Heron) | √(s(s−a)(s−b)(s−c)), s = (a+b+c)/2 | sides 3, 4, 5 m = 6 m² |
| Circle | π × (diameter / 2)² | 2 m diameter = 3.14 m² |
| Trapezoid | (a + b) / 2 × h | (6 + 4) / 2 × 3 = 15 m² |
For flooring, tiles or paint, the area is only the first step - see the flooring calculator, tile calculator and paint calculator, which add waste and coverage.
Measuring a flat or house
Measure each room separately and add them up. Example: a 4 × 3.5 m living room (14 m²), a 3.2 × 3 m bedroom (9.6 m²) and a 2 × 1.5 m bathroom (3 m²) give 26.6 m². Split irregular rooms into rectangles and triangles and measure at floor level along the walls.
Practical tips: measure each wall twice (at both ends), because walls are rarely perfectly parallel, and use the larger value when buying materials. Ignore skirting boards, but decide in advance whether to include built-in wardrobes, kitchen units or a bath - for flooring you usually skip them, for painting the ceiling you do not. Results are rounded to two decimal places, which is about 100 cm² - more precision than a tape measure delivers.
Square metres and square feet
The calculator works in metres and centimetres. If your plans are in feet, convert the result: 1 m² = 10.764 sq ft and 1 sq ft = 0.0929 m². Example: a 20 m² room is 20 × 10.764 = 215.3 sq ft. You can also convert each dimension first - 12 ft = 3.66 m - with the length converter, then enter it here. Converting lengths before multiplying is more accurate than rounding a sq ft total.
Ares, hectares and cm²
- 1 are (a) = 100 m² (a 10 × 10 m square).
- 1 hectare (ha) = 100 ares = 10,000 m² (100 × 100 m).
- 1 m² = 10,000 cm².
Example: a 30 × 40 m plot is 1,200 m², which is 12 ares or 0.12 ha. In centimetres: 250 × 400 cm = 100,000 cm² = 10 m².
Frequently asked questions
How do I calculate the square metres of a room?
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How many square metres in a hectare?
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How do I calculate an L-shaped room?
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How do I convert cm² to m²?
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How do I convert square metres to square feet?
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How do I find the area of a triangle from its sides?
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