Area in one step, in metric or imperial
Whether you are buying flooring, comparing apartments or ordering turf, you need the area of a surface. In the US people usually think in square feet (ft²), while most of the world uses square metres (m²). Product labels can use either, so this calculator accepts measurements in feet, inches, yards, metres, centimetres or millimetres and always shows both systems.
Formulas for the three basic shapes
rectangle or square: area = length × width
triangle: area = base × height ÷ 2
circle: area = π × diameter² ÷ 4 (or π × radius²)
The height of a triangle is measured at right angles to the base, not along a sloping side.
Example 1 – a bedroom: 12 ft × 10 ft = 120 ft². In metric that is 11.15 m².
Example 2 – a triangular garden bed: base 3 m, height 2 m. Area = 3 × 2 ÷ 2 = 3 m² (32.3 ft²).
Example 3 – a round patio: diameter 4 m. Area = 3.1416 × 16 ÷ 4 = 12.57 m² (135.3 ft²).
Converting between square feet and square metres
Converting area is not the same as converting length. One foot is 0.3048 m, but one square foot is 0.3048 × 0.3048 = 0.0929 m².
m² = ft² × 0.092903
ft² = m² × 10.7639
1 square yard = 9 ft² = 0.836 m²
| Area | Square feet | Square metres |
|---|---|---|
| Small bathroom | 40 ft² | 3.7 m² |
| Bedroom | 120 ft² | 11.1 m² |
| Two-car garage | 400 ft² | 37.2 m² |
| Average US home | 2,300 ft² | 214 m² |
| Tennis court (doubles) | 2,808 ft² | 260.9 m² |
Measuring irregular rooms
Few rooms are perfect rectangles. Split an L-shaped room into two rectangles, calculate each one and add them together. For a room with a bay window, measure the main rectangle and add the bay as a rectangle plus two triangles. If a room has a chimney breast or built-in cupboard you won’t cover, subtract that area. The number of identical areas field lets you multiply one shape, for example four identical walls or six identical windows.
Practical tips
- Measure twice at different points; old walls are rarely straight. Use the largest measurement for materials.
- Mixing units? Convert everything to the same unit first. 12 ft 6 in is 12.5 ft.
- Add waste. Tiles, laminate and wallpaper need extra for cutting, typically 5–15%. The flooring calculator works out boxes including waste.
- Painting? The paint calculator uses wall height and room size to estimate litres or gallons.
- Need volume instead? For soil, gravel or concrete use the cubic meter calculator.
Square meters for common projects
Area is the starting point for almost every home project. Paint coverage is quoted in square meters or square feet per liter or gallon, so you need the wall area minus doors and windows. Flooring, tiles and carpet are sold per square meter or square foot, usually with a waste allowance on top; the flooring calculator adds that for you. Lawn seed, turf and fertilizer are dosed per square meter, and heating and cooling capacity is often estimated from the floor area of a room. Rental prices and property listings are also compared per square meter or square foot, so knowing the exact area helps you judge whether an asking price is reasonable.
Frequently asked questions
How do I calculate the area of a room in square feet?
Measure the length and width in feet and multiply them. A 15 ft × 12 ft room is 180 ft². For measurements in inches, divide the result by 144 to get square feet.
How do I convert square feet to square metres?
Multiply by 0.0929. For example, 1,000 ft² × 0.0929 = 92.9 m². To go the other way, multiply square metres by 10.764.
How many square feet are in a square yard?
Nine, because a yard is three feet and 3 × 3 = 9. Carpet is sometimes still sold by the square yard in the US.
How do I find the area of a circle?
Multiply π (3.1416) by the radius squared, or by the diameter squared and divide by four. A circle with a 10 ft diameter has an area of 78.5 ft².
What if my room is L-shaped?
Divide it into rectangles, calculate each area separately and add the results together.
Last reviewed: 2026-10-06. Results are estimates for information only.