Almost all U.S. LTL carriers use NMFC freight classes, although some are attempting to move to a dimensionally-based system.
Freight Class 500 freight is the most expensive to ship. This classification is reserved for items of very high value or for items that use lots of space but weigh very little.
Multiply the length, width, and height of your shipment, then divide the total weight of your package by that number. If your shipment is 4 feet long, 5 feet wide, and 4 feet tall, you would multiply 4 x 5 x 4 to get 80 cubic feet. If it weighs 800 pounds, you would divide 800 / 80 to get 10 pounds per cubic foot.