Circle Calculator
Calculate the area and circumference of a circle from its radius.
How to use this tool
- Enter radius in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your area and the full breakdown beneath it.
Calculate the area (πr²) and circumference (2πr) of a circle from its radius.
Frequently asked questions
- How do you calculate circle area and circumference?
- Area = π × r², Circumference = 2 × π × r, where r is the radius and π ≈ 3.14159.