The diameter of a circle is the distance from a point on the circle to a point pi radians away, and is the maximum distance from one point on a circle to another. The diameter of a sphere is the maximum distance between two antipodal points on the surface of the sphere.


If r is the radius of a circle or sphere, then d=2r. The ratio of the circumference C of a circle or great circle of a sphere to the diameter d is pi,


See also

Brocard Diameter, Circumference, Circumradius, Circumsphere, Generalized Diameter, Graph Diameter, Pi, Polygon Diameter, Radius, Sphere, Transfinite Diameter Explore this topic in the MathWorld classroom

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Cite this as:

Weisstein, Eric W. "Diameter." From MathWorld--A Wolfram Web Resource.

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