Calculate the volume of a refrigerator by measuring the length, width and height of the refrigerator's interior in inches. Multiply the three figures together and convert to feet to arrive at the number of cubic feet.
For example, if a refrigerator's interior measures 2 feet long by 3 feet wide by 6 feet high, the volume of the refrigerator interior is 36 cubit feet. Measure additional compartments in the same way. Manufacturers sometimes include the volume of door compartments in the total volume of a refrigerator's interior. This figure is often referred to as the usable interior of an appliance.