Use this circumference calculator to compute a circle's radius, diameter, and area from its circumference.
Circumference calculator
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Using the calculator
Enter the circumference and select your units. The calculator instantly computes the radius, diameter, and area in the same units. Supported units include millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles.
Use the Diameter, Radius, Circumference, or Area buttons to switch between calculation modes. Click Show Advanced Options to access arc length, chord length, sector area, and segment area calculations.
What is circumference?
The circumference of a circle is the total distance around its edge. Imagine wrapping a string around a circle and measuring its length.
Circle formulas
Given the circumference, you can find all other circle dimensions:
d = c / \pi
r = c / (2\pi)
a = c^2 / (4\pi)
