Different types of products have different freight shipping costs associated with them. The motor carrier industry defines products being shipped according to certain characteristics: density, stowability, handling and liability. Each definition, or description, is called a freight classification.

A shipment`s freight class is needed in order to calculate freight charges. Usually shippers who frequently send freight shipments by ltl will know the class of their freight. Additionally, there is a reference called the National Motor Freight Classification (NMFC) to determine classes for freight rating purposes.