Shape Area Calculator
Calculate a rectangle, triangle, or circle
Supported shapes and formulas
A rectangle uses A = length × width. A triangle uses A = base × perpendicular height ÷ 2. A circle uses A = π × radius².
Enter the dimensions
Select the shape first. Then enter the first dimension and, for a rectangle or triangle, the second one. Values are interpreted as metres; the result is shown in square metres and square feet.
Triangle example
A 6 m base and a 4 m perpendicular height produce 6 × 4 ÷ 2 = 12 m². A sloped side length is not a substitute for perpendicular height.
Irregular areas
Split a composite area into rectangles, triangles, and circular parts. Calculate and add the pieces, subtracting openings. This calculator does not perform that decomposition automatically.
Frequently Asked Questions
Which dimensions does a rectangle need?
Enter length and width in the same unit. The area is length multiplied by width.
How is triangle area calculated?
Enter a base and its perpendicular height. The calculator multiplies them and divides by two.
How is circle area calculated?
Select circle and enter the radius as the first dimension. The second field is ignored.
Must all dimensions use the same unit?
Yes. The calculator interprets entries as metres and returns square metres plus square feet.
How do I calculate a composite area?
Split it into supported shapes, calculate each area, then add or subtract the parts.
How many decimal places should I keep?
The result shows two decimals. Keep more precision in measurements when rounding could materially affect the final area.