Math · NUMORA
Circle Calculator
Radius → area, circumference, diameter.
Open interactive calculatorHow to use
Radius to area, circumference and diameter.
Formula
A = πr²; C = 2πr
FAQ
Is this Circle calculator accurate?
The formula and assumptions are shown on the page, and the engine is covered by audit tests. Results are for reference — not financial or medical advice.
Do I need an account?
No. Calculations run in your browser. Recents can stay on this device.
What inputs do I need?
Radius to area, circumference and diameter.
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