Find all the measurements of the object you're working with. If you're measuring a square-shaped box, for example, use the tape measure to find the length, width and height of the box. Because you are trying to find the cubic inch measurement, you need to find these basic measurements in inches.
Multiply your object's length by its width. The number you get is the square inch measurement of the object.
Convert square inches into cubic inches by multiplying your previous calculation by the height of the object. The number you get is the total number of square inches in the volume of that object.