Circle Calculator
Calculate the area, circumference, and diameter of a circle from its radius.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Enter a circle's radius to calculate its area, circumference, and diameter.
Your result
153.938
Area
Circumference43.982
Diameter14
AI explanation
Formula
Area = πr²; Circumference = 2πr; Diameter = 2rWorked example
Circle with radius 7
| Field | Value |
|---|---|
| Radius | 7 |
| Area | 153.938 |
| Circumference | 43.9823 |
| Diameter | 14 |
Assumptions
- Uses the standard value of π (3.14159...).
Frequently asked questions
How is the area of a circle calculated?
Area = π × radius², where π (pi) is approximately 3.14159.
What's the difference between circumference and perimeter?
They mean the same thing for a circle — "circumference" is just the specific term used for a circle's perimeter (the distance around it).
How do I calculate area from diameter instead of radius?
Divide the diameter by 2 to get the radius, then enter that here — or use Area = π × (diameter/2)².