Circle Calculator

Calculate radius, diameter, circumference, and area of a circle by entering any one value.

Input Data

Select the known value and enter it below to calculate the other properties of the circle.

Choose known value:

Results

Understanding Circle Properties

A circle is a fundamental shape in geometry defined as the set of all points in a plane that are at a constant distance (the radius) from a central point. Key properties include:

Radius (r): The distance from the center to any point on the circle.
Diameter (d): The distance across the circle through the center, equal to 2r.
Circumference (C): The distance around the circle, calculated as \(C = 2\pi r\) or \(C = \pi d\) .
Area (A): The space enclosed within the circle, calculated as \(A = \pi r^2\) .

This calculator helps you quickly find these values, making circle calculations easy and efficient for various applications in mathematics, engineering, and everyday life.