Circle Calculator
Radius, diameter, circumference, area from any input
📚 Learn more — how it works, FAQ & guide Click to expand
Learn more — how it works, FAQ & guide
Click to expand
Free circle calculator
Enter any one property of a circle — we calculate the rest.
How to use this tool
- 1
Enter any one value
Radius, diameter, circumference, or area.
- 2
All others auto-fill
Any property of a circle uniquely determines the others.
Frequently Asked Questions
Formulas used
d = 2r, C = 2πr, A = πr². Any one value gives us r, and from r all the others.
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100% Privacy. This tool runs entirely in your browser. Your data is never uploaded to any server.