Know to circle

Calculator

Enter the radius, diameter, circumference or area of a Circle to find the other three. The calculations are done "live":

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How to Calculate the Area

The area of a circle is:

π (Pi) times the Radius squared:A = π r²

or, when you know the Diameter:A = (π/4) × D²

or, when you know the Circumference:A = C² / 4π


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