What is the shell method in calculus?

The shell method in calculus is a procedure for finding the volume of a solid revolving around an axis. This method is also referred to as the method of cylindrical shells.

The shell method typically involves a graph with bounds. Often, the shape is bounded by either the x or y axis and a function. Solving by the shell method involves taking an integral over the area covered on the graph. For example, if the shape extends from 0 to 2 on the x axis, then it would be integrated from 0 to 2. The integral of this function is multiplied by 2 times pi.