Free OnlineCalculators & Converters
Circumference Calculator
Calculate the circumference, area, diameter, arc length, and sector area of a circle from radius or diameter. Instant results with formulas shown.
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Key Features — Circumference Calculator
Circumference from radius or diameter
Circle area calculation
Arc length for any angle
Sector area calculation
Visual circle diagram
All formulas displayed
Why Use This Tool — Circumference Calculator
Free Online Circumference calculatorCircle calculator — for EveryoneFast & Easy Circumference of a circleDiameter to circumference — 100% FreeFree Online Radius to circumference
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Frequently Asked Questions — Circumference Calculator
What is the circumference of a circle?
Circumference is the distance around the outside of a circle. Formula: C = 2πr (where r is the radius) or C = πd (where d is the diameter). For a circle with radius 5: C = 2 × π × 5 ≈ 31.416.
How do I find circumference from diameter?
Multiply the diameter by π (pi ≈ 3.14159). Circumference = π × diameter. For a diameter of 10: C = π × 10 ≈ 31.416. The radius is always half the diameter.
What is the area of a circle?
The area of a circle is A = πr², where r is the radius. For a circle with radius 5: A = π × 5² = π × 25 ≈ 78.54 square units.