Freight class is a standardized classification system created by the National Motor Freight Traffic Association (NMFTA). It is used in the trucking industry to group shipments into categories based on four factors: density, stowability, handling, and liability. Each shipment is assigned a number from 50 to 500, where lower numbers (like 50) represent dense, easy-to-handle freight with lower shipping costs, and higher numbers (like 500) are for light, bulky, or fragile items that cost more to ship. Understanding your freight class is key to getting accurate shipping quotes and avoiding unexpected fees.
The Origin of Freight Class and the NMFC
In the early 20th century, the trucking industry needed a consistent way to compare different types of freight and set fair shipping rates. The National Motor Freight Classification (NMFC) was developed to provide a uniform classification system. It evaluates thousands of commodities and groups them into 18 freight classes (from 50 to 500) based on their transport characteristics. The NMFC is updated regularly to reflect changes in materials, packaging, and logistics. Today, nearly all less-than-truckload (LTL) carriers use the NMFC class to determine shipping prices.
Why Freight Class Matters for Your Shipping Costs
The most important reason to know your freight class is cost. Carriers use the class to set rates, usually per hundredweight (CWT). Dense products (e.g., steel, bricks) fall into lower classes like 50 or 55. Their compact size means they take up less space, so carriers can fit more in a trailer, which lowers the cost per pound. Light but bulky items (e.g., pillows, empty plastic bins) have higher classes (200–500) because they take up a lot of room relative to their weight, reducing the trailer's efficiency and raising the price. Getting your class wrong can lead to reclassification fees, delayed shipments, or even denied claims if the carrier discovers an error.
Density is the primary factor in determining freight class. The formula is simple: Density (lbs/cu ft) = Weight (lbs) ÷ Volume (cubic feet). You can find a detailed breakdown of the Freight Class Density Formula on our site. For example, a shipment with a density of 20 lbs/cu ft falls into class 70 (15–22.5 lbs/cu ft range). If your density is just under a threshold, the class jumps to the next higher number, increasing cost.
How Freight Class Is Used in the Shipping Process
To determine your shipment's freight class, you start by measuring its length, width, and height (in inches), then calculate volume in cubic feet (divide by 1728 if using inches). Next, weigh the shipment (in pounds). Divide weight by volume to get density. Then cross-reference the density with the Freight Class Ranges 50-500 table to find the corresponding class. Our How to Calculate Freight Class guide walks through this step by step.
Most LTL carriers require you to declare the NMFC class on the bill of lading. If you are unsure, you can use the car… (Note: I stopped because the response is cut off. I'll provide the rest in the final output.)
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