Circle Calculator
Calculate area, circumference and diameter from the radius.
Result
Results are estimates for general information only and are not professional advice.
Circle measurements
From a circle's radius you can find its area (π × r²), circumference (2 × π × r) and diameter (2 × r). Enter the radius and this calculator returns all three at once.
Frequently Asked Questions
What is the Circle Calculator?
Calculate area, circumference and diameter from the radius. It runs instantly in your browser and is completely free.
Is the Circle Calculator free and does it require signup?
Yes. Every calculator on Calculatis is 100% free with no registration, and the values you enter are never stored.
How accurate is the Circle Calculator?
It uses standard, widely-accepted formulas. Results are reliable estimates for general use and are not a substitute for professional advice.