Circle Area Calculator
Calculate circle area instantly from radius, diameter, or circumference with interactive visualization.
1. Select Known Metric
2. Enter Value & Unit
radius
Results
Radius(r)Input
d / 2
0.0000cm
Diameter(d)
2 × r
0.0000cm
Circumference(C)
2 × π × r
0.0000cm
Area(A)
π × r²
0.0000cm²
Formula calculations verified.Pi constant: 3.1415926535...