Area Calculator

Calculate the area of rectangles, circles, triangles and more.

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How it works

Pick a shape — rectangle, square, circle, triangle, parallelogram, or trapezoid — and enter its dimensions. The tool applies the right geometry formula (length × width for a rectangle, π r² for a circle, half base times height for a triangle, and so on) to compute the area. It shows the formula it used so you can follow the math. Useful for flooring, gardening, and homework. All calculation runs locally in your browser.

rectangle = l × w     circle = π r²     triangle = ½ b h

Common use cases

  • Finding the square footage of a room for flooring.
  • Calculating the area of a circular patio or garden bed.
  • Checking a geometry homework answer.

Frequently asked questions

Which shapes are supported?

Rectangle, square, circle, triangle, parallelogram, and trapezoid. Each uses its standard area formula, which the tool shows alongside the result.

What units does it use?

It is unit-agnostic — enter your dimensions in any single unit and the area comes out in that unit squared (for example metres in gives square metres).

How is the circle area calculated?

Using π times the radius squared. If you have the diameter, halve it first to get the radius.