How to use this circle calculator
Enter the requested values above and select Calculate. The result updates immediately on the page, so you can change one value and compare different scenarios without leaving the calculator.
Formula and method
Circumference = 2πr. Area = πr².
Example
A circle with radius 5 has circumference about 31.416 and area about 78.540 square units.
What this calculator is useful for
Calculate circumference and area from a circle radius. It is designed for quick estimates and everyday problem solving. When a calculation affects a contract, tax filing, medical decision or other high-stakes situation, verify the result with the appropriate professional or authoritative source.
Frequently asked questions
What does the Circle Calculator calculate?
Calculate circumference and area from a circle radius.
How does the calculation work?
Circumference = 2πr. Area = πr².
Is this calculator free?
Yes. ERICH Calculators is free to use and no account is required.