How to figure box size

To figure out how big a box is measure the Height, Width, and Depth of the box (in inches) then HxWxD / 1728 will give you the cubic ft. of the box. Usually you will be concerned with the airspace inside the box so be sure to get the inside measurements  and not the outside measurements for your calculations.

How to figure angles

To calculate a truckbox or one with a simple angle, measure Height, Width, Top depth and Bottom depth. and use the formula (HxWx(TD+BD)/1728)/2 to convert it to cubic Ft.

For more than one angle you will have to measure and calculate sections and then add the sections together for your total.