Small Circle
Radius: 2 cm; Diameter: 4 cm
Radius (from diameter): 2 cm; Area (using radius): 12.56636 cm²; Area (using diameter): 12.56636 cm²
Area of a Circle Calculator
Math0.0(0)
Calculates the area of a circle given its radius or diameter.
More tools:Math & Statistics Calculators
How To Use
How to use this calculator
Start with your values, or try a preset.
Step 1
Enter Radius and Diameter in the units shown.
Step 2
Read Radius (from diameter), Area (using radius), and Area (using diameter) in the results panel. Results update as you change the inputs.
Step 3
Choose a preset to load an example, then adjust the values for your situation.
Worked Examples
Example calculations
See the inputs and their calculated results.
Medium Circle
Radius: 5 cm; Diameter: 10 cm
Radius (from diameter): 5 cm; Area (using radius): 78.53975 cm²; Area (using diameter): 78.53975 cm²
Large Circle
Radius: 10 cm; Diameter: 20 cm
Radius (from diameter): 10 cm; Area (using radius): 314.159 cm²; Area (using diameter): 314.159 cm²
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