Circle Calculator
Calculate radius, diameter, circumference, and area of a circle. Free online tool with interactive charts and comparison tables.
Step 1: Circle Measurements
5.0
Circle formulas
Diameter = 2 × radius
Circumference = 2π × radius
Area = π × radius²
π ≈ 3.14159
Step 2: Units & Display
Visualization
The doughnut chart compares circle area (blue) to the area of the bounding square (red).
Circle Results
Summary
Radius comparison
Formulas & chart
Area of the circle
78.5 cm²
Radius = 5.0 cm
Radius
5.0 cm
Diameter
10.0 cm
Circumference
31.4 cm
Area
78.5 cm²
Circle properties for different radii
| Radius | Diameter | Circumference | Area |
|---|
Area grows with radius
Key formulas
r = radius , d = diameter , C = circumference , A = area
d = 2r
C = 2πr
A = πr²
π ≈ 3.14159265359
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