Circle Calculator
Calculate area, circumference, and diameter. Enter values for instant results with step-by-step formulas.
Formula
Area = πr² | C = 2πr
Area depends on the square of the radius. Circumference is the linear distance around the edge.
Worked Examples
Example 1: Radius 5
Problem:r=5
Solution:Area = π×5² ≈ 78.54. Circumference = 2×π×5 ≈ 31.42.
Result:A: 78.54, C: 31.42
Example 2: Diameter 10
Problem:d=10
Solution:r = 10/2 = 5. Same as above.
Result:A: 78.54
Frequently Asked Questions
How do I find the area of a circle?
Use the formula A = πr². If you have the diameter, divide it by 2 to get the radius first, then square it and multiply by π.