The circumference formula
Circumference = 2 * pi * radius, or equivalently pi * diameter. Both formulas give the same result since diameter = 2 * radius.
C = 2 * pi * r = pi * d
Two equivalent ways to express circumference.
Circumference Calculator
Calculate the circumference of a circle from radius or diameter with area and other properties.
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Also in Circles
Geometry
Circumference of a circle from radius or diameter
Calculate the circumference (perimeter) of a circle from its radius or diameter. The result includes the area and other circle properties.
Limitations
Applies to perfect circles only.
Frequently asked questions
10 * pi ≈ 31.42 units.
Yes. Circumference is the specific term for the perimeter of a circle.
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