Use this area calculator to compute a circle's radius, diameter, and circumference from its area.
Circle area calculator
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Using the calculator
Enter the area and select your units. The calculator instantly computes the radius, diameter, and circumference in the corresponding linear units. Supported units include square 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 area?
The area of a circle is the total space contained within its boundary. It's measured in square units.
Circle formulas
Given the area, you can find all other circle dimensions:
r = \sqrt{a / \pi}d = 2\sqrt{a / \pi}c = 2\sqrt{\pi a}
