What is freight class based on and how do I determine the right class for my shipment?

Freight class (1–500 scale, 18 classes) is assigned by the National Motor Freight Traffic Association (NMFTA) based on four characteristics:

1. Density (weight per cubic foot — the most important factor):

• < 1 lb/cu ft → Class 500 (highest rate)
• 1–2 lb/cu ft → Class 400
• 30–35 lb/cu ft → Class 70
• > 50 lb/cu ft → Class 50 (lowest rate)

2. Stowability: Can it be stacked? Loaded with other freight? Irregularly shaped cargo costs more.
3. Handling: Fragile, hazardous, or awkward cargo that requires special handling = higher class.
4. Liability: High-value goods susceptible to theft or damage = higher class.

How to determine your class:

1. Look up your product's NMFC code at nmfta.org (paid subscription) or ask your broker
2. Calculate density: weight (lbs) ÷ volume (cubic feet). Volume = L×W×H in inches ÷ 1,728.
3. Use the <a href="https://calculatecbm.com/freight-class">freight class calculator</a> to get the class from density

What happens if you get it wrong:
Carriers inspect freight on delivery. If they reclassify (upgrade to higher class), you receive a Freight Bill Correction adding 15–30% to your cost. Intentional misdescription can result in carrier claims or blacklisting.