How to use the Area Calculator
- Choose the shape and the unit you measured in.
- Enter the measurements. The boxes change to match the shape: side for a square, length and width for a rectangle, radius for a circle, and base and height for a triangle.
- Press Calculate to get the area, the perimeter (or circumference), and the area converted to square metres and square feet.
Area formulas
| Shape | Area | Perimeter |
|---|---|---|
| Square | side × side | 4 × side |
| Rectangle | length × width | 2 × (length + width) |
| Circle | π × radius2 | 2 × π × radius |
| Triangle | ½ × base × height | sum of the three sides |
The calculator uses the full-precision value of π (3.14159265…), not a rounded 3.14.
Worked examples
Square, side 5 m: 5 × 5 = 25 m².
Rectangle, 8 m by 6 m: 8 × 6 = 48 m².
Circle, radius 7 m: π × 7 × 7 = 153.94 m².
Triangle, base 10 m and height 6 m: ½ × 10 × 6 = 30 m².
Common area conversions
| Unit | Equal to |
|---|---|
| 1 square metre (m²) | 10.7639 square feet |
| 1 square foot (ft²) | 0.092903 square metres |
| 1 square yard (yd²) | 9 square feet = 0.836127 square metres |
| 1 square inch (in²) | 6.4516 square centimetres |
| 1 square kilometre (km²) | 1,000,000 square metres |
Everyday uses
- Flooring and tiles: floor area ÷ area of one tile gives the number of tiles. Add 5 to 10% for cuts and wastage.
- Painting: wall area tells you how much paint to buy once you know the coverage printed on the tin.
- Plots and gardens: compare plot sizes in one unit before comparing prices.
- Fabric and crafts: work out how much material a project needs.
Common mistakes to avoid
- Mixing units. Do not enter a length in centimetres and a width in metres. Convert first, or measure both in the same unit.
- Using the diameter as the radius. A circle’s radius is half its diameter.
- Forgetting the square. Area is in square units, so 5 m by 5 m is 25 m², not 25 m.
Frequently asked questions
Which unit should I use?
Use whichever unit you measured in. The result is given in that unit squared, and also in square metres and square feet so you can compare quickly.
How do I find the area of an irregular shape?
Split it into squares, rectangles, triangles and circles, find each area, and add them up. For land measured in gunthas or acres, use a dedicated land-area converter.
What is the difference between area and perimeter?
Area is the amount of surface a shape covers, measured in square units. Perimeter is the distance around its edge, measured in plain length units.
Which value of pi does the calculator use?
It uses the full-precision value your browser provides (about 3.141592653589793), so results are not affected by rounding π to 3.14.
How do I convert square feet to square metres?
Multiply square feet by 0.092903 to get square metres. This calculator shows both values for every result.
I know the diameter of a circle. How do I find its area?
Halve the diameter to get the radius, then use π × radius × radius. A circle with a 14 m diameter has a 7 m radius and an area of about 153.94 m².
How do I find the area of a triangle if I only know the three sides?
This tool uses base and height. If you only have the three sides, you can first find the height, or use Heron’s formula: area = √(s(s−a)(s−b)(s−c)) where s is half the perimeter.