Circle Area Calculator
Calculate circle area from radius, diameter, circumference, or known area, then recover radius, diameter, circumference, and area.
Circle area from one known value
English competitors usually let users enter one known circle value and recover the rest. This calculator accepts radius, diameter, circumference, or known area, then returns radius, diameter, circumference, and area.
A is area; r is radius.
d is diameter.
C is circumference.
Input modes and units
| Known value | What the calculator does |
|---|---|
| Radius | Calculates area, diameter, and circumference directly. |
| Diameter | Divides diameter by two to recover radius first. |
| Circumference | Recovers radius from circumference first. |
| Known area | Uses reverse calculation to recover radius and linear values. |
Frequently Asked Questions
Sources and References
Calculations are based on the listed reference sources. Links open in a new tab.
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