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.

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.

Density is the relationship between weight and size. A ping pong ball, which is very little material surrounding a good amount of air, is low density. Bricks, which are heavy for their size, are high density. In LTL shipping, it is commonly measured in pounds per cubic foot.