Area and Perimeter of a Circle - Geometry Calculator

An online calculator to calculate the area A and perimeter P of a circle given its radius r. The formulas for the perimeter P and area A of a circle are given by:

P = 2 π r
A = π r 2

How to use the calculator


Enter the radius r as a positive real number and press "calculate". The outputs are the area and perimeter of the circle.

r =

P =
A =

More References and links

Grade 8 Problems and Questions on Circles with Answers
Online Geometry Calculators and Solvers