The formula for calculating cubic inches depends on the geometric shape. For example, the formula for the volume of a rectangular solid is length x width x height, while the formula for a pyramid is (1/3) x base x height, according to Math.com.
Formula tables for calculating volume can be found online at sites like Math.com and Basic-mathematics.com. In addition, there are calculators that will allow you to plug in the dimensions of the solid so you can find the volume, such as Calculator.net. It is important that you convert all of the dimensions of your solid to inches before using a formula or calculator to find the volume in cubic inches.