National Motor Freight Classification (NMFC) is a freight classification system created by the National Motor Freight Traffic Association (NMFTA) and used for interstate, intrastate, and foreign commerce shipping of LTL cargo. NMFC freight codes provide standardized freight classes to determine the ease of transport of many of the huge variety of different commodities being shipped together in LTL shipments every year.

The class determines the cost of the shipping. The lower the class, the lower the cost.

No. While density is one of the primary factors in determining NMFC freight class, other factors, such as value, are also used in making that determination. Gold bars, for example, are very dense, but they fall into shipping class 500 along with very low-density items because of their high value.