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)

Calculate the area of common shapes: circle, rectangle, triangle, and trapezoid.

Calculate triangle area, perimeter, and angles from three side lengths using Heron's formula and the law of cosines.

Calculate circle area, circumference, diameter, and radius. Solve from any known value.

Calculate the area, perimeter, and apothem of a regular hexagon from its side length.