The National Motor Freight Classification (NMFC) is a standard that provides a comparison of goods(commodities) moving interstate, intrastate and internationally. Commodities are grouped into one of 18 classes ranging from 50 to 500 based on four transportation characteristics:
Density being the most important factor in determining a freight class. The more dense the product is the lower the freight class. Class 50 is the least expensive and 500 is the most costly. The NMFC also includes rules and packaging requirements for each type of commodity being shipped, to ensure there is sufficient packaging for products that could possibly shift or move while in transit.
The National Motor Freight Classification guide is used by shippers, carriers, third party logistics to properly rate shipments moving interstate and via intrastate transport in North America. When shipping your product, extra care is required to select the correct freight class, otherwise the carrier hauling the goods is under obligation to re-classify the shipment, which ultimately could result in higher freight costs.
Knowing what you are shipping, what it is made out of and its end use, will allow your shipment to be classified correctly. Your service provider will classify the shipment based on the description you show on the bill of lading (bol). Often they will refer to the customs documents for additional information. A couple key details are what the product is made of (wood, plastic, metal) and what is its end use. If they are unable to classify based on information provided they will contact you.
If your shipment's class relies exclusively on density, then it is extremely important to provide accurate dimensions and weight of your shipment. Any variance in either of these two will effect the density(pounds per cubic foot) therefore resulting in a different class and freight rate. Guessing dimensions and weight is not a wise decision. All carriers will re-weigh a shipment if questionable, and re measure for an accurate freight classification. Also note, if you have shipped a product for 20 years at the same class, there is a good chance that your product may have been re-classified under a new ruling.
The NMFC is updated on a yearly basis, as some products may be reclassified by the board. The 18 classes are: 50, 55, 60, 65, 70, 77.5, 85, 92.5, 100, 110, 125, 150, 175, 200, 250, 300, 400 and 500.
When in doubt contact your service provider for assistance on classifying freight.