Maths & numbers
Circle calculator
Find a circle’s area, diameter and circumference from its radius.
A clear answer. Here’s how.
Area = πr², diameter = 2r and circumference = 2πr. Length outputs use your input unit; area uses its square.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Radius (in any length unit)
- 5
Example result
- Area (square units)
- 78.5398163397
- Diameter
- 10
- Circumference
- 31.4159265359