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

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.

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 …

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

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 …

Area of a circle, formula for area explained with examples, pictures, interactive examples and quiz.

This guide explains how to calculate a circle's area, the formulas used, and walks you through using our free online circle area calculator to solve geometry problems quickly and accurately.