Circle Circumference Calculator

The circumference of a circle is 2π times its radius (C = 2πr), or π times its diameter. A wheel with a 35 cm radius rolls about 2.2 meters per revolution.

This measure is used for bike wheel sizing, fencing round areas, and estimating material lengths for round tables or pools. The constant π (approximately 3.14159) is precisely the ratio of any circle's circumference to its diameter. See also the circle area calculator for the surface inside.