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2D Geometry Calculator (Area & Perimeter)

Quickly compute area and perimeter for rectangles, circles, triangles, trapezoids, and regular polygons.

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How to use (3 steps)

  1. Select the shape you want to work with.
  2. Enter the dimensions using any consistent unit.
  3. Check the area and perimeter below, then adjust values to explore.

Use with height for the ½ × base × height formula.

Add both legs to get the perimeter.

Use either side length, apothem, or circumradius. If you enter several, they must match the same polygon.

Select a shape and enter the required dimensions to see the area and perimeter here.

FAQ

Which shapes can I calculate?

The tool covers rectangles, circles, triangles, trapezoids, and regular polygons. Enter the dimensions requested for each shape to get area and perimeter.

Do I need to specify units?

Use whatever units you prefer. The calculator keeps everything consistent, so if you enter centimetres the area will be in square centimetres and the perimeter in centimetres.

What do I enter for a regular polygon?

Provide the number of sides (3 or more) plus at least one of the following: side length, circumradius, or apothem. Missing values are derived automatically.

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