How to Calculate Freight Class
Freight class is the backbone of LTL (Less-Than-Truckload) shipping pricing in the United States. The National Motor Freight Traffic Association (NMFTA) assigns classes from 50 to 500 based primarily on density — the relationship between a shipment's weight and its volume.
Freight Density Formula
The density calculation is simple:
Density (lbs/ft³) = Total Weight (lbs) ÷ Total Volume (ft³)
Where volume in cubic feet = (Length × Width × Height in inches) ÷ 1,728
For example, a pallet measuring 48" × 40" × 48" weighing 500 lbs has a volume of 53.33 ft³ and a density of 9.38 lbs/ft³, placing it in Class 100.
Why Freight Class Matters
Incorrect classification leads to reclassification fees, which can add 20-50% to your shipping costs. Carriers routinely inspect shipments, and if the actual class differs from what was declared, you'll pay the difference plus a fee. Using this calculator helps you avoid surprise charges.
Tips for Lowering Your Freight Class
- Use stackable industrial containers to maximize density per cubic foot
- Eliminate void space in packaging — tight packing increases density
- Palletize shipments using standard pallet sizes for best stowability
- Consider CBM calculations when shipping internationally