How this area calculator works
Area is the amount of flat space a shape covers, measured in square units. Every shape has its own formula, but they all build on the same idea: multiply lengths together and, for triangles and trapezoids, take a fraction of the result. Pick a shape above, type its measurements in any single unit, and the area updates as you type.
For straight-sided shapes the perimeter is the total distance around the outside. For a circle that distance is called the circumference (2πr), and for an ellipse it can only be approximated, so this tool shows the area only. Because the unit you choose is just a label, remember to enter every measurement in the same unit — the area is then reported in that unit squared.
Area formulas by shape
| Shape | Area formula | Also shown |
|---|---|---|
| Rectangle | length × width | Perimeter 2 × (L + W) |
| Square | side² | Perimeter 4 × side |
| Circle | π × r² | Circumference 2πr |
| Triangle | ½ × base × height | — |
| Parallelogram | base × height | — |
| Trapezoid | ½ × (a + b) × h | — |
| Ellipse | π × a × b | — |
Reference note: a square is a rectangle with equal sides, so entering the same length and width gives side². The ellipse formula uses the two semi-axes (half the full width and half the full height).
Frequently asked questions
- How do I calculate the area of a circle?
- The area of a circle is π × r², where r is the radius. Square the radius and multiply by pi (about 3.14159). A circle with a 5 m radius has an area of π × 25 ≈ 78.54 m².
- What is the area of a rectangle?
- The area of a rectangle is length × width — multiply the two side lengths. A rectangle 4 m by 3 m covers 12 m². A square is the special case where the sides are equal, so its area is side².
- How do I find the area of a triangle?
- The area of a triangle is ½ × base × height, with the height measured at a right angle to the base. A triangle with a base of 6 m and height of 4 m has an area of ½ × 6 × 4 = 12 m².
- What is the formula for the area of a trapezoid?
- The area of a trapezoid is ½ × (a + b) × h, where a and b are the parallel sides and h is the perpendicular distance between them. Add the parallel sides, multiply by the height, then halve it.
- How do I calculate area for flooring / a room?
- For a rectangular room multiply length by width — 5 m × 4 m = 20 m² — and add a little for cuts and waste. For L-shaped rooms, split the space into rectangles, find each area, then add them together.
- What units is area measured in?
- Area is measured in square units: the length unit squared. Metres give square metres (m²), feet give square feet (ft²), centimetres give cm² and inches give in².