Circle Calculator
Radius
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Diameter
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Circumference
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Area
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How It Works
This circle calculator uses established formulas to provide accurate results.
The basic rule:
- Diameter = 2 × radius
- Circumference = 2πr = πd
- Area = πr²
- Radius from area: r = √(A/π)
Results are estimates. Consult a professional for critical decisions.
Frequently Asked Questions
What is the relationship between radius and diameter?
The diameter is always twice the radius: d = 2r. Conversely, the radius is half the diameter: r = d/2.
What is pi (π)?
Pi is the ratio of a circle's circumference to its diameter. It is approximately 3.14159 and is an irrational number, meaning it goes on forever without repeating.
How do you find circumference from area?
First find the radius from the area using r = √(A/π), then calculate circumference using C = 2πr.
What is the formula for circumference?
Circumference = 2πr or equivalently Circumference = πd, where r is the radius and d is the diameter.