Area Calculator
Shape
Area50.0000
This area calculator finds the two-dimensional surface enclosed by a chosen shape — rectangle, triangle, circle, trapezoid, or ellipse — using the standard geometric formula for each. Pick a shape, supply the dimensions it needs, and the tool returns the area in square units of whatever unit you entered. It is handy for flooring, land, fabric, and any planning task that depends on surface coverage.
Formula
Rectangle = l·w; Triangle = ½·b·h; Circle = π·r²; Trapezoid = ½·(a+b)·h; Ellipse = π·a·b
- l, w
- Length and width of a rectangle
- b, h
- Base and perpendicular height (triangle, or the height of a trapezoid)
- r
- Radius of a circle
- a, b
- The two parallel sides of a trapezoid, or the two semi-axes of an ellipse
How it works
- Select a shape: rectangle, triangle, circle, trapezoid, or ellipse. The required dimension fields change to match the shape you choose.
- Enter the measurements — length and width for a rectangle, base and height for a triangle, radius for a circle, the two parallel sides plus height for a trapezoid, or the two semi-axes for an ellipse.
- The calculator applies the matching formula and shows the area rounded to four decimal places in square units of your input unit.
Worked examples
Find the area of a trapezoid with parallel sides of 6 and 10 and a height of 4.
- Add the parallel sides: 6 + 10 = 16.
- Multiply by the height and halve: ½ × 16 × 4 = 32.
The trapezoid area is 32 square units.
Find the area of an ellipse with semi-axes of 5 and 3.
- Multiply the semi-axes by π: π × 5 × 3 = 15π.
- Evaluate: 15 × 3.14159… ≈ 47.1239.
The ellipse area is about 47.1239 square units.
Frequently asked questions
- What units does the area come out in?
- The result is in square units of whatever unit you typed in. If you enter dimensions in metres the area is in square metres; enter feet and you get square feet.
- How do I find the area of a triangle if I only know its three sides?
- This tool uses base and height for triangles. If you only have the three side lengths, use Heron’s formula instead, which is available in the dedicated triangle calculator.
- Why does the circle use only a radius and not a diameter?
- The circle area formula π·r² is defined in terms of the radius. If you only know the diameter, divide it by two first, or use the circle calculator which accepts the diameter directly.
- What is the difference between a circle and an ellipse here?
- A circle is a special ellipse where both semi-axes are equal to the radius. The ellipse option lets you set two different semi-axes, so a 5-by-3 ellipse is wider in one direction than the other.