Circle Circumference Calculator

Q: "How do I find the circumference of a circle?"

"C = 2πr (radius r) or C = πd (diameter d). π ≈ 3.14159."

Q: "What is the formula for circumference?"

"Circumference = 2 × π × radius, or π × diameter."

Q: "Can I enter radius or diameter?"

"Yes. Choose \"Radius\" or \"Diameter\" and enter the value. The calculator gives the circumference."

Q: "What units can I use?"

"Any length unit (meters, feet, inches). The result is in the same unit."

Q: "What is π?"

"π (pi) is the ratio of a circle's circumference to its diameter, approximately 3.14159."

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.