As previously stated, what is measured is the difficulty of shipping the goods (I.e. transportability of those goods.)

Key terms:

1. Density;

2. Stowability, which includes excessive weight or excessive length;

3. Ease or difficulty of handling, which includes special care or attention necessary to handle the goods; and

4. Liability, which includes value per pound, susceptibility to theft, liability to damage, perishability, propensity to damage other commodities with which transported and propensity to spontaneous combustion or explosion.

A description of these four characteristics will help aid your quote provider with the necessary information to determine your shipping class.

The NMFC assigns a number from 50 to 500 based on an evaluation of these four characteristics. There is no need for the shipper to be aware of this number, only that the type of his or her shipment will affect the price of the shipment.  As your freight class increases, the price of shipping in bulk significantly decreases.

The NMFC publication describes the nature of these classifications to a much fuller depth, explaining it all, down to the formulas used to calculate these costs.  The NMFC publication is referred to by both carrier and quote provider in order to assess the varying complexities of shipping your goods, helping each provide their quote. 

The complexity of understanding the formulas which negotiate your freight class, factoring in the many different characteristics needed to indicate the appropriate assigned class, is what a freight quote provider can use to obtain your freight class and freight quote.

Reference: click here.