Circle Calculator
Enter radius, diameter or circumference and get every other property of the circle.
Circle Calculator
Enter radius, diameter or circumference and get every other property of the circle.
How to use the Circle Calculator
- Choose "By radius", "By diameter" or "By circumference".
- Enter the value.
- Click Calculate.
Formula
C = 2πr = πd
A = πr²
d = 2r
Example
Radius 10: Diameter = 20, Circumference ≈ 62.832, Area ≈ 314.159.
Step-by-step calculation
- Diameter: 2 × 10 = 20.
- Circumference: 2 × π × 10 = 62.832.
- Area: π × 10² = 314.159.
Real-world uses
- Circular garden and pool planning.
- Wheel and gear calculations.
- Pipe and duct sizing.
Common mistakes
- Confusing radius and diameter.
- Using diameter in the area formula (which needs radius).
- Squaring π instead of multiplying by π.
Frequently asked questions
What is π (pi)?
Pi ≈ 3.14159265. It is the ratio of a circle's circumference to its diameter.
How accurate is the result?
The calculator uses a high-precision value of π and rounds cleanly.
Can I find circumference from area?
Yes. r = √(A/π), then C = 2πr. The "by circumference" mode also works.