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Area of Circle Calculator - Circle Calculator
Free circle calculator to find area, circumference, radius, and diameter. Enter any value and calculate all circle properties instantly.
Circle Calculator
Calculate area, circumference, and more
Circle Properties
Enter your values to see results
and click the "Calculate" button
Circle Formulas
A circle is a perfectly round shape where every point on its boundary is the same distance from the center. This calculator finds all circle properties from any single measurement using the mathematical constant π (pi ≈ 3.14159).
How to Use This Calculator
- Enter any one value: radius, diameter, circumference, or area
- Click Calculate
- Get all other circle properties instantly
Circle Formulas
Area = πr², Circumference = 2πr
Where r is radius and π ≈ 3.14159. Diameter = 2r.
Frequently Asked Questions
What is pi (Ï€)?
Pi is the ratio of a circle's circumference to its diameter. It's approximately 3.14159 and is an irrational number that never ends or repeats.
How do I find radius from area?
Use the formula r = √(A/π). If area is 78.54, then r = √(78.54/3.14159) = √25 = 5.
What's the difference between radius and diameter?
Radius is the distance from center to edge. Diameter is the distance across the circle through the center. Diameter = 2 × Radius.
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