Circle Calculator
Calculate a circle’s area, circumference and diameter from its radius.
How it works
Circumference is the distance around a circle; area is the space enclosed.
Formula and assumptions
This calculator uses the values and units shown above. Results are rounded for display. Confirm inputs and assumptions before relying on a result for academic, engineering or other important decisions.
Example
Try the sample values, calculate, then change one input at a time to see how the result changes.
Frequently asked questions
Are results exact? They depend on the selected formula, input values and rounding. Special cases are reported when possible.
Does this replace professional software? No. Independently verify results for safety-critical or formal work.
For educational and general information. Report an issue.