Circle Area & Circumference Calculator

Enter a circle's radius to compute its area, circumference, and diameter.

Inputs
Results
Area
78.54 sq units
Circumference
31.42 units
Diameter
10 units

Try an example

Formula

Area = πr², Circumference = 2πr

Learn How This Works

Circle and Triangle Area Formulas, Explained With Real Shapes

The area formulas for circles and triangles (including Heron's formula) worked through with real numbers.

Frequently Asked Questions

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