Circle Area Calculator

The area of a circle equals π times the radius squared (A = πr²). A circle with a 5 cm radius has an area of about 78.54 cm². If you only know the diameter, halve it first to get the radius.

Circle areas come up in gardening (round beds), cooking (pizza sizes — a 30 cm pizza is more than double a 20 cm one!) and construction. Related tools compute the circumference of a circle and the volumes of spheres and cylinders that build on this formula.