Calculate the circumference of a circle from its radius or diameter.
Circle Measurements
Calculated Diameter
10.0000
Circumference Result
31.4159units
Circumference (C)
The total distance around the edge of the circle.
Area78.5398
Diameter10.0000
C = 2πr
About this calculator
Quick Reference
Pi (π)≈ 3.14159
RadiusHalf Diameter
CircumferencePerimeter of Circle
What is Circumference?
Circumference is the linear distance around the outside of a circle. It is directly proportional to both the radius and the diameter. The ratio of any circle's circumference to its diameter is the mathematical constant π (pi).
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Pro Tips
If you know the radius, multiply by 2π.
If you know the diameter, multiply by π.
The result is a linear measurement (e.g., cm, inch, m).
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Fun Facts
"Archeologists have found circles and wheels in human settlements dating back over 5,000 years."
"If you walk along the Equator of the Earth, you're walking the Earth's circumference (approx. 24,901 miles)."
"The symbol π was first used by William Jones in 1706."
