What is the formula for the area of a circle?

Area = π × r². The circumference (perimeter) is 2 × π × r. Use π ≈ 3.14159.

How do I find the area of a triangle?

Area = ½ × base × height. The height must be perpendicular to the base. If you know all three sides instead, use Heron's formula: s = (a+b+c)/2, then Area = √(s(s−a)(s−b)(s−c)).

What is the difference between area and perimeter?

Area measures the surface inside a shape (in square units: cm², m², ft²). Perimeter measures the total length of the boundary (in linear units: cm, m, ft).

How do I calculate the area of an irregular shape?

Break it into simpler shapes (rectangles, triangles, circles), calculate each area separately, then add them together. This is the basis of numerical integration.

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Area calculator

Pick a shape, enter its dimensions — get area and perimeter instantly. Five shapes supported.

Length

Width

Area

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Perimeter

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