The number of dimples on a golf ball varies, depending on the manufacturer and may even be different for different models made by the same manufacturer. The dimples are usually the same size as one another, but some golf balls have several different sizes of dimple on the same ball. Any number between 300 and 500 dimples is reasonable, and 336 is a common number. Not just any number will do. Golf balls are usually covered with dimples in a highly symmetrical way, and for many values of N, it is impossible to cover the golf ball uniformly without gaps. Symmetry is important or the ball will wobble or its flight will depend on which part of the ball is forwards or sideways as the ball spins. You can get an idea of how to space dimples uniformly around a sphere by thinking about the "platonic solids" -- the tetrahedron, cube, octahedron, dodecahedron and icosahedron, and placing a dimple at the corners of an inscribed platonic solid. Variations on this theme give the corners of Buckminster Fuller’s geodesic domes, and also the possible symmetrical locations of dimples on a golf ball.
If you’re curious about why the dimples are there in the first place, see our answer.
(republished on 07/19/06)