The National Motor Freight Traffic Association (NMFTA) publishes a list of freight class designations, codes, and subclasses for commonly shipped items (https://classit.nmfta.org/). A subscription fee is required to access this list. You can learn more about freight classes from the experts at Koho for free on our freight classes pages.
The first step in determining your freight class is to take measurements. Measure the height, width and depth of your shipment then multiple those three measurements together for the total cubic feet. Then divide the total cubic inches by 1,728 (the number of cubic inches in a cubic foot). Finally, divide the weight (in pounds) of the shipment by the total cubic feet.
Some items, such as car transmissions, have a specific class no matter how heavy or big they are. This is called a fixed class. Items can be assigned a fixed class if the value and transportability very rarely change.