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 ? r

A = ? 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.