Floor Area Calculator
Add up the floor area of up to four rectangular rooms or sections, in square metres, square feet and square yards.
The total floor area of the rooms you measure.
How the floor area calculator works
Each rectangular room or section is length × width; the total is the sum. Split L-shaped rooms into two rectangles and enter each. The result is shown in square metres, square feet and square yards, since flooring, paint and rent are quoted in all three.
Measure at floor level along the longest points; for quotes, most trades use the gross area and let their own waste allowances handle the rest.
Formula: area = Σ (length × width)
Worked examples
| Inputs | Total floor area | Note |
|---|---|---|
| 5 × 4 m room | 20 | 20 m² = 215 sq ft |
| 5 × 4 m plus 3 × 3 m | 29 | 29 m² |
| 16 × 13 ft room | 208 | 208 sq ft = 19.3 m² |
FAQFrequently asked questions
How do I measure an L-shaped room?
Split it into two rectangles at the inside corner and enter each as a room. Any shape made of right angles can be split this way.
How many square feet in a square metre?
10.764. A square yard is 0.836 m².
Do I measure the walls or the floor?
The floor, between the finished wall surfaces, for flooring and carpet. Property listings often quote a larger figure measured to the outside of external walls.
What about triangular or curved rooms?
A right-angled triangle is half the enclosing rectangle — enter the rectangle and halve the result, or pin it and compare.
Where these figures come from
- The Engineering ToolBox — material densities, coverage and unit data — bulk densities, concrete at 2,400 kg/m³, board and sheet sizes
- Brick Development Association — brick sizes and quantities — 215 × 102.5 × 65 mm, 60 bricks per m²
- UK Government — Approved Documents (Building Regulations) — Building Regulations guidance
Last checked: September 2026. Coverage rates and material sizes are typical manufacturer figures — check the product you buy.