Circle Calculator
Calculate the area and circumference of a circle from its radius.
Result
78.54
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Formula
Area = πr² | Circumference = 2πrCircle Calculator
The area of a circle is π times the radius squared. The circumference is 2π times the radius. The diameter is twice the radius.
Common Use Cases
Circle calculations are fundamental in geometry, engineering (pipe and cable sizing), architecture, manufacturing (turning and milling), physics (orbital mechanics), and everyday tasks like calculating the area of a round garden or the circumference of a wheel.
Tips for Accurate Results
- The radius is half the diameter. If you know the diameter, divide by 2 first.
- Area uses π × r² (radius squared), while circumference uses 2 × π × r (radius, not squared).
- For quick estimates, use π ≈ 3.14 or π ≈ 22/7.
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