Circle Calculator

Enter any single known parameter (radius, diameter, circumference, or area) to calculate all other circular measurements, sector areas, and arc lengths.

Circle Mathematics & Constant π

A circle is the set of all points in a plane equidistant from a fixed center point. The ratio of any circle's circumference to its diameter is always equal to the mathematical constant π (pi ≈ 3.14159265359).

Frequently Asked Questions

How do you find the radius from the area?

Since Area = πr², rearranging gives r = √(Area / π). Taking the square root of area divided by pi yields the radius.

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