Sphericity

Sphericity is a measure of how closely the shape of an object resembles that of a perfect sphere.

Sphericity is a specific example of a compactness measure of a shape.

Sphericity applies in three dimensions; its analogue in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft, is called roundness.

, of an oblate spheroid (similar to the shape of the planet Earth) is: where a and b are the semi-major and semi-minor axes respectively.

Hakon Wadell defined sphericity as the surface area of a sphere of the same volume as the particle divided by the actual surface area of the particle.