Circle Circumference Calculator
Calculate circle circumference from radius or diameter. Example: radius 5 → circumference 31.42. Formula C = 2πr or πd. Copy result.
The circumference of a circle is the distance around it. Formula: C = 2πr (using radius r) or C = πd (using diameter d), where π ≈ 3.14159. Enter the radius or diameter and choose which one you entered. The calculator gives the circumference in the same unit. Copy the result or Copy with labels.
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Examples
- radius 5 → C ≈ 31.42
- diameter 10 → C ≈ 31.42
- radius 1 → C ≈ 6.28
FAQ
How do I find the circumference of a circle?
C = 2πr (radius r) or C = πd (diameter d). π ≈ 3.14159.
What is the formula for circumference?
Circumference = 2 × π × radius, or π × diameter.
Can I enter radius or diameter?
Yes. Choose "Radius" or "Diameter" and enter the value. The calculator gives the circumference.
What units can I use?
Any length unit (meters, feet, inches). The result is in the same unit.
What is π?
π (pi) is the ratio of a circle's circumference to its diameter, approximately 3.14159.