Math & Science
Circle Calculator
Calculate circle area, circumference, diameter
Created and maintained by: CalcTago Editorial TeamLast updated: 2026-02-13
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
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Frequently asked questions
What does the Circle Calculator do?
It helps you calculate circle area, circumference, diameter.
What inputs do I need?
Enter Radius.
Are decimals supported?
Yes, you can use decimal values where appropriate.
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About this tool
This Circle Calculator turns your inputs into practical results. Provide Radius to calculate Area and Circumference.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.