Circle Calculator
Given a radius, diameter, circumference, or area, compute the other circle measures.
Enter one known value
Tips: Choose what you know, enter one positive value, then press Calculate.
FAQ
The tool uses the JavaScript constant Math.PI, a double-precision approximation of π.
C = 2πr, so r = C/(2π).
No. If your input implies a negative radius or impossible area, the calculator will not show a result.