The National Motor Freight Classification (NMFC) is the freight classification system devised by the National Motor Freight Traffic Association (NMFTA) and is used for all interstate, intrastate, and foreign commercial movement of LTL cargo. NMFC codes provide standardized freight classes to determine the ease of transport of many of the wide variety of commodities that are shipped together in LTL shipments.
Your freight cost is determined by a number of variables, such as how far your shipment needs to go, the freight class number, whether or not accessorials are needed, as well as fluctuating fuel costs and truck capacity.
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.