Calculate all circle properties including area, circumference, radius, and diameter with step-by-step solutions
Enter value in linear units
Diameter
d = 2r
Circumference
C = 2πr = πd
Area
A = πr²
π ≈ 3.14159
2π ≈ 6.28318
π² ≈ 9.86960
√π ≈ 1.77245
The diameter is always twice the radius: d = 2r. The radius is the distance from the center to the edge, while the diameter is the distance across the circle through the center. If you know one, you can easily find the other.