Formulas
- Diameter: d = 2r
- Circumference: C = 2πr = πd
- Area: A = πr² = πd² / 4 = C² / (4π)
Circle calculator
Enter any one of radius, diameter, circumference or area. The other three are derived automatically.
Radius (r)
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Diameter (d)
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Circumference (C)
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Area (A)
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