Circle Calculator
Use this free circle calculator to work out the area, circumference, radius and diameter of a circle from any one of them. Enter your numbers and the results update as you type. It runs in your browser, so nothing you enter is uploaded, and there is nothing to sign up for.
Runs in your browser. Your files never leave your device.
How it works
- 01Enter your numbers in the fields.
- 02The results update as you type.
- 03Change a value to compare what-if cases.
Questions
What are the circle formulas?
Area is pi times r squared, circumference is 2 times pi times r, and the diameter is twice the radius.
Is my data saved or sent anywhere?
No. The calculation runs in your browser and nothing is uploaded.
Are the results exact?
The maths is exact for the values you enter, but real life can differ because of fees, taxes and changing rates. Use the result as a guide.
Is my file uploaded to a server?
No. Everything happens inside your browser on your own device. Your files are never sent to us or anyone else.
Is it free?
Yes. It is free to use, with no signup, no watermark and no daily limit.