Description: See the volume formula for a sphere used in an example where we are given the diameter of the sphere. Created by Sal Khan and Monterey Institute for Technology and Education. Find the volume of a sphere with a diameter of 14 centimeters. But the formula for the volume of a sphere is volume is equal to 4/3 pi r cubed, where r is the radius of the sphere. And just like for circles, the radius of the sphere is half of the diameter.*Teacher Advisor is 100% free.