The area of a circle calculator will compute the surface of a circle using a radius or a diameter.

Aug 1, 2025 · Use this circle calculator to find the area, circumference, radius or diameter of a circle. Given any one variable A, C, r or d of a circle you can calculate the other three unknowns.

This calculator computes the values of typical circle parameters such as radius, diameter, circumference, and area, using various common units of measurement.

See How to Calculate the Area below, but first the calculator: Enter the radius, diameter, circumference or area of a Circle to find the other three.

Area of circle calculator using formulas A = πr², A = πd²/4, and A = C²/4π. Calculate area of a circle instantly from radius, diameter, or circumference with step-by-step solutions.

In geometry, the area enclosed by a circle of radius r is πr2. Here, the Greek letter π represents the constant ratio of the circumference of any circle to its diameter, approximately equal to 3.14159.

Calculate the area of a circle given the radius, diameter, or circumference. Plus learn the formulas and steps to find a circle's area.

Jul 2, 2025 · This calculator determines the area of a circle using either the radius or the diameter. You may also enter a custom value for π, or use the default value of 3.14159.

Free online area of a circle calculator which helps you calculate the are of any circle, given its radius. Supports many different metrics such as in, ft, yd, mm, cm, meters, etc.

Oct 29, 2025 · To find the area of a circle, use the formula A = π • r2, where r is the radius of the circle. If you only know the diameter of the circle, then use the formula A = π • (d/2)2 where d is diameter.