About this calculator
The calculator uses π to full precision, not 22/7.
How to use it
- Choose what you know.
- Enter it.
- Read the rest.
The formula
Area = πr²; circumference = 2πr; diameter = 2r
- π
- ≈ 3.14159
Worked example
Radius 7
- Area = π × 49 ≈ 153.94.
- Circumference ≈ 43.98; diameter 14.
What the result means
22/7 is a handy school value but slightly larger than π.
Assumptions
- All lengths in the same unit.
Limitations
- Results are rounded to 10 significant figures.
Frequently asked questions
What is the area of a circle?
πr².
How do I find the radius from the circumference?
Divide by 2π.
Is π equal to 22/7?
No, 22/7 is an approximation.
Last reviewed on 3 October 2026. Found a mistake? Tell us.