Runs locally
Circle Calculator
Area and circumference from the radius.
Ctrl+Enter runs. Ctrl+Shift+Backspace clears.
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Uses π for the disk area and the circumference.
About this tool
Enter the radius of a circle and get its area and circumference at once. Handy for geometry homework, cutting materials or estimating the size of a round table.
How to use it
- 01
Enter the radius of the circle.
- 02
Read the area, calculated as πr².
- 03
Read the circumference, calculated as 2πr.
FAQ
Frequently asked questions
How do I use the diameter instead?
Divide the diameter by two and enter that value as the radius.
Which value of π is used?
Full double-precision π, so results are accurate to many decimal places.