The conversion formula
Diameter = circumference / pi. Radius = circumference / (2 * pi). These are direct rearrangements of the circumference formula C = pi * d.
Circumference to Diameter Calculator
Convert a known circumference to the corresponding circle diameter, radius, and area.
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Also in Circles
Geometry
Convert circumference to diameter and radius
The circumference-to-diameter calculator converts a known circumference to the corresponding circle diameter and radius. It also shows the circle area.
Limitations
Applies to perfect circles only. The circumference must be a positive number.
Frequently asked questions
Approximately 10. 31.42 / pi ≈ 10.
Yes. Wrap a string around the object, mark where it meets, then measure the string length. This gives the circumference.
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