Circumference Calculator
Circle circumference from radius or diameter.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Circumference
- 37.6991
- Diameter
- 12
- Area
- 113.0973
- Radius
- 6
Working
- 1C = 2π × 6 = 37.6991
Quick answer
Circumference equals 2πr, or πd if you know the diameter.
C = 2πr = πd
How to use the Circumference Calculator
- 1Enter the radius of the circle.
- 2Read the circumference and area.
- 3Halve the diameter first if that is what you have.
Frequently asked questions
What is π?
The ratio of circumference to diameter, about 3.14159.
How do I get radius from circumference?
Divide by 2π.