Circumference Calculator
Calculate the circumference (perimeter) of a circle from its radius or diameter.
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Circumference
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Area
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Diameter
Recent Calculations
What Is Circumference?
The circumference of a circle is the distance around its edge, equivalent to the perimeter of the circle.
Formula
C = 2πr = πd, where r is radius and d is diameterExample
A circle with radius 5 has a circumference of 2π × 5 = 31.4159 units.
Frequently Asked Questions
What's the formula for circumference?
C = 2πr (using radius) or C = πd (using diameter), where π ≈ 3.14159.
How do I find circumference from area?
C = 2√(πA), where A is the area.