How this calculator works
Enter the values for radius. The result applies the displayed method and rounds only for presentation.
Formula / method
Diameter = 2r; circumference = 2πr; area = πr².
Worked example
Worked example: Radius = 5.
Assumptions and limitations
The inputs use the units shown and the displayed circle calculator method applies to the situation being estimated.
This circle calculator uses the stated formula and supplied units; unusual inputs, local rules or professional context can change the interpretation.