Freight Class Guide

What Is Freight Class?

Freight class is a standardized rating system established by the National Motor Freight Traffic Association (NMFTA) and published in the National Motor Freight Classification (NMFC) tariff. It assigns every commodity a class between 50 and 500. The higher the class, the more expensive it is to ship per hundredweight in the LTL system.

Class exists because LTL carriers are pricing the use of trailer space, not just weight. A pallet of foam packing material weighs almost nothing but fills a third of a trailer. A pallet of steel bolts weighs 2,000 pounds but takes up six inches of floor space. Treating these identically by weight alone would destroy carrier economics. Freight class is the mechanism that accounts for this difference.

The Four Classification Factors

Every NMFC class rating is determined by evaluating a commodity across four characteristics:

Density: pounds per cubic foot. This is the primary determinant for most commodities. Low-density freight (under 1 lb/cu ft) earns class 400-500; high-density freight (over 50 lb/cu ft) earns class 50-55. Calculate density by dividing total weight by total cubic feet.
Stowability: how easily the freight can be loaded with other shipments. Hazardous materials, unusually shaped freight, or items that cannot be stacked reduce stowability and increase class.
Liability: risk of theft, damage, or damage to other freight. High-value electronics, fragile goods, or perishables carry higher liability ratings and therefore higher classes.
Handling: special handling requirements. Freight requiring special equipment, refrigeration, or careful placement costs more to handle and receives a higher class.

Class Ranges and What They Mean

As a practical reference for the most common shipping classes:

Class 50-55: dense, durable commodities: bricks, sand, metals, flour. Most favorable rates.
Class 65-85: car parts, machinery, bottled beverages, boxed books. Mid-range rates.
Class 92.5-100: computers, electronics, refrigerators. Higher rates reflecting liability.
Class 125-175: sheet metal, small appliances, clothing in boxes. Premium rates.
Class 200-300: low-density items like mattresses, flat-screen TVs, wood cabinets.
Class 400-500: very low-density or very high-liability freight. Rates at this level often make LTL economically non-viable. FTL or cargo van may be more cost-effective.

How to Look Up Your Freight Class

The authoritative source is the NMFC tariff, which requires a subscription through the NMFTA. For most shippers, the practical path is:

Use the Warp freight class calculator. Enter commodity type, weight, and dimensions to get the class.
Contact your carrier or 3PL and ask for the NMFC item number that applies to your commodity. Every commodity has a specific item number in the tariff.
Weigh and measure every shipment accurately before tendering. Estimated weights are the single most common cause of re-weigh disputes.

Re-Weigh and Reclassification Disputes

When a carrier believes the BOL class or weight is incorrect, they inspect the freight at the destination terminal and issue a freight bill correction. This correction applies retroactively. You receive it after delivery, when you have no leverage. The charge includes the rate difference at the corrected class plus an inspection fee.

To dispute a reclassification, you must submit a written protest with the original BOL, proof of weight (certified scale ticket), and documentation supporting the original class assignment. Carriers are not required to reverse the charge without evidence. The protest process can take 30-90 days and requires dedicated staff time to manage at volume.

This is one of the core reasons high-volume shippers migrating to per-pallet pricing report immediate reductions in invoice dispute workload. The classification variable is removed from the billing equation entirely.

When LTL Class Stops Mattering

Freight class is a construct of the LTL tariff system. It does not apply to full truckload (FTL) shipments, where you are buying trailer space rather than sharing it. It also does not apply to per-pallet-priced LTL networks where pricing is structured by pallet position rather than NMFC class.