Circle Calculator Guide
Use this calculator for quick circle measurements.
Important Note
The tool will use the radius first if both radius and diameter are provided.
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Circle Calculator
Circle calculator for area and circumference from radius or diameter.
Geometry
Fast Calculation
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Circle Calculator
Enter a radius or diameter to calculate circle area and circumference instantly.
Result
0
Ready to calculate
Working
Formula
Area = πr² and circumference = 2πr.
Use Case
Useful for geometry, design, and radius-based measurements.
Tip
If diameter is entered, the calculator automatically converts it to radius.