Circle Calculator

Find a circle's diameter, circumference, and area from its radius.

Your inputs

Enter your information and select Calculate to see the result.

Diameter is twice radius; circumference is 2πr; area is πr².

Change one assumption at a time to see which inputs have the greatest effect on the estimate.

A radius of 2 has area about 12.5664.

This calculator is for educational use; verify important work independently.

Review this educational estimate against current quotes, official information, and your own budget before making a financial decision.