Circle Calculator
Find area, circumference, radius and diameter from any one of them. The result updates as you type, with the working underneath so you can check it.
Your details
Result
Area
78.5398
- Radius
- 5
- Diameter
- 10
- Circumference
- 31.4159
Good to know: A = πr², C = 2πr
About this tool
Formula
A = πr², C = 2πr
Questions people ask
What is pi?
The ratio of a circle's circumference to its diameter, about 3.14159.
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How we calculate this
We use the standard published formula or definition for this calculation, and we show the working so you can check it.
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