The perimeter is the total distance around the outside of a two-dimensional shape.

How do you find a circle's perimeter?

A circle's perimeter is called circumference: C = 2 x pi x r.

Perimeter Calculator

Select a shape and enter its dimensions to calculate the perimeter. Supports rectangles, triangles, circles (circumference), and regular polygons.

Shape

Length / Side a / Radius / Side

Width / Side b / (unused) / Number of Sides

Side c (triangle only)

Perimeter

Formula Used

P = 2(l + w) = 2(10 + 5)

Last updated: April 16, 2026

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