For freight classified under a density-based NMFC item, density is the number that determines the applicable freight class — and therefore a major part of the rate. The good news: the math is simple, and once you can do it, you can predict and control your classification.
The density formula
Density is weight per cubic foot:
Density (lbs/ft³) = Total weight (lbs) ÷ Total volume (ft³)
To get the volume of a pallet in cubic feet, multiply its dimensions in inches and divide by 1,728 (the number of cubic inches in a cubic foot):
Volume (ft³) = (Length × Width × Height in inches) ÷ 1,728
A worked example
Say you have one pallet measuring 48" × 40" × 48", weighing 600 lbs.
- Volume = (48 × 40 × 48) ÷ 1,728 = 92,160 ÷ 1,728 = 53.3 ft³
- Density = 600 ÷ 53.3 = 11.3 lbs/ft³
On the current NMFC density scale (effective July 19, 2025), ~11.3 lbs/ft³ lands in the 10–12 bracket — class 92.5. Increase the weight to 1,000 lbs on the same pallet and density jumps to ~18.8 lbs/ft³, dropping you into the 15–22.5 bracket at class 70 — a much cheaper rating.
Measure to the extremes
Carriers measure the outermost points of the shipment, including the pallet and any overhang. If a box sticks out past the pallet edge, or a piece is stacked crooked, that extra space counts against you — it lowers your density and can push you into a higher class. Always measure the real, as-shipped footprint.
Packaging mistakes that raise your class
- Oversized boxes with empty space. Air is expensive in LTL. Right-size your packaging.
- Overhang past the pallet. Even a couple of inches changes the billable dimensions.
- Tall, light stacks. Height with low weight tanks your density.
- Guessing instead of measuring. Estimated dimensions on the BOL are the #1 cause of reweigh/re-class adjustments.
Remember: density isn't always the whole story
Some commodities are classified under a fixed NMFC item regardless of density. Calculate density to understand the rate impact, but always confirm the actual NMFC item and its rule before you book — see What Is Freight Class? for how the two interact.