Shape calculator
Choose rectangle, circle, or triangle. Values are unit-agnostic, so use one consistent length unit and read area in the corresponding squared unit.
Enter values and calculate to see the formula here.
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Formulas
Area = width × height. Perimeter = 2 × (width + height).
Area = πr². Circumference = 2πr. Results using π are shown as practical decimal approximations.
Perimeter is the sum of the three sides. Area uses Heron’s formula after confirming the three lengths satisfy the triangle inequality.
Any two triangle sides must add to more than the third side. If that condition fails, the lengths cannot form a non-degenerate triangle.
It is unit-agnostic. If lengths are in centimetres, perimeter is in centimetres and area is in square centimetres; the same pattern applies to other consistent units.
Keep checking
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