What Is Freight Class? NMFC Classification Explained

What is freight class and who sets it?

The National Motor Freight Traffic Association (NMFTA), headquartered in Alexandria, Virginia, publishes and maintains the NMFC. The NMFTA is the standards body for US LTL freight pricing. Carriers are not making up class numbers -- they are bound by the NMFC tariff, which is updated periodically to reflect commodity changes and industry input.

The NMFC assigns a class number to each commodity type. You look up your commodity in the NMFC directory, find the class for your specific item and packaging, and declare that class on the bill of lading.

What are the 18 NMFC freight classes?

There are 18 freight class tiers, running from class 50 at the low end to class 500 at the high end. Lower class numbers mean lower shipping rates. Higher class numbers mean higher rates per hundredweight (CWT, or per 100 lbs).

How do the four NMFC classification factors work?

The four factors that determine freight class are density, stowability, handling, and liability.

Density is the most influential factor for most commodities. A shipment that is heavy relative to its size earns a low class because it fills trailer space efficiently. A light, bulky shipment wastes cubic space and earns a high class.

Stowability covers whether your freight can be stacked or loaded alongside other freight. Hazardous materials, oddly shaped items, and products that cannot bear weight on top all push the class up.

Handling reflects how difficult it is to move the freight. Standard palletized boxes are easy. Fragile items, oversized pieces, or cargo that requires special equipment costs the carrier more labor and increases the class.

Liabilityaccounts for the carrier's exposure if your freight is lost, stolen, or damaged. High-value electronics, food products, and perishables typically fall into higher classes.

Most everyday commodities are primarily classified by density, with the other three factors creating exceptions or adjustments to the base class.

Why does freight class affect your shipping cost?

LTL carriers price by hundredweight (CWT) -- a rate per 100 pounds of freight. That base rate varies by class. Higher freight classes correspond to lower-density or higher-risk cargo and result in higher shipping rates per hundredweight.

If two shipments weigh the same but one is class 50 and the other is class 250, the class 250 shipment can cost three to four times more, depending on the carrier's tariff. That gap exists because lower-density freight takes up more trailer space per pound, which means the carrier is moving less revenue-generating weight in the same truck.

What is the difference between freight class and freight classification?

These terms are often used interchangeably but have a technical distinction.

Freight class is the specific number (50, 65, 100, etc.) assigned to your shipment.

Freight classification is the broader process of determining that number -- applying the four NMFC factors, looking up the commodity in the NMFC directory, and assigning the correct class tier. When a carrier reclassifies your shipment after pickup, they are repeating that process using actual measured dimensions and weights instead of your declared values.

How do you determine the correct freight class for your shipment?

There are three ways:

1. Look up the NMFC item number. Every commodity in the NMFC has an item number. Licensed brokers, freight management systems, and some carrier websites let you search by product description to find the assigned class.
2. Calculate density and use the density table. For many commodities, density is the deciding factor. Measure length x width x height in inches, divide by 1,728 to get cubic feet, then divide weight in pounds by cubic feet to get density. Match that density to the class table above.
3. Use a freight class calculator. The OnSumo freight class calculator handles the density calculation automatically -- enter your dimensions and weight and it returns the class in seconds.

How does a freight class calculator find the class automatically?

A freight class calculator applies the density formula -- (length x width x height in inches) / 1,728 to get cubic feet, then weight / cubic feet to get density -- and maps the result to the NMFC class table. The OnSumo freight class calculator does this in one step: enter your pallet or box dimensions and total weight, and the tool returns the class, the density, and the cubic footage.

The calculator is accurate for density-based classification. If your commodity has a special NMFC exception, verify the NMFC item number directly. For a deeper dive into the density formula itself, see how to calculate freight density.

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