Understanding LTL Freight Density & NMFC Classification
How carriers calculate dimensional weight, density tiers, and how to avoid costly re-bills on your bill of lading.
What is NMFC Freight Class?
The National Motor Freight Classification (NMFC) is a standardized indexing system published by the National Motor Freight Traffic Association (NMFTA). Class codes run from Class 50 (highest density, lowest transport cost) to Class 500 (lowest density, highest transport cost).
LTL (Less-Than-Truckload) carriers rely on freight class to determine shipping rates based on four transportability characteristics: density, handling, stowability, and liability. For general freight, density (pounds per cubic foot or PCF) is the primary rating factor.
Density does not reach every class code. Under NMFC Docket 2025-1, effective July 19, 2025, the density scale has 13 subprovisions spanning Class 400 down to Class 50. Classes 77.5, 110, 150, 200 and 500 are still valid NMFC classes, but they are assigned by commodity-specific listings on handling, stowability or liability grounds rather than by density, so a density calculator will never return one.
How LTL Freight Density (PCF) is Calculated
Freight density measures how heavy a shipment is relative to the volume of trailer space it consumes:
Always measure the maximum exterior dimensions including the pallet height, handles, straps, or cargo overhangs. Carriers verify dimensions with automated 3D laser scanners at sorting hubs!
The Carrier Bounding Box & Overhang Rule
LTL carriers do not calculate irregular cargo contours. They bill based on the smallest rectangular box envelope that completely encloses the shipment from floor to ceiling.
- Cargo Overhang: If a crate overhangs a 40" pallet by 2 inches on each side, the billable width jumps to 44 inches.
- Cylinders & Drums: A 55-gallon drum is measured as a square bounding box (D × D × H), because adjacent cargo cannot occupy the corner voids around the cylinder.
- Pallet Height: Standard wooden pallets add ~6 inches to total billed vertical height and ~40 lbs to gross weight.
Why "Bump Weight" No Longer Works
NMFC Item 171, the "bumping" clause, once let a shipper construct a density artificially by stating weight the freight did not have, in order to reach a lower class. The Commodity Classification Standards Board eliminated it at NMFTA's June 2019 public meeting. The carrier bulletins issued for the change put it plainly: "All references to item 171 are removed from individual items. The artificial construction of density to obtain a lower class is cancelled," effective August 24, 2019.
The bill of lading has to carry the real figures. 49 CFR 373.101 requires the receipt or bill of lading to show the number of packages, the description of the freight, and the "weight, volume, or measurement of freight (if applicable to the rating of the freight)". Carriers also reweigh and re-dimension on the dock, so an overstated weight is found and rebilled rather than saving anything.
What still lowers a class is real density: tighter packing, a shorter stack, less overhang, or consolidating handling units. The Density Threshold Advisor shows the PCF each next subprovision begins at, and how much actual weight or how much less billed cube it takes to reach it.
NMFC Density Class Table — 13 Subprovisions (Docket 2025-1, effective July 19, 2025)
| Freight Class | Density Range (PCF) | Typical Commodity Examples | Transport Cost Tier |
|---|---|---|---|
| Class 50 | 50 PCF or greater | Steel fasteners, metal ingots, dense machinery, lead weights | Lowest Rate (Cheapest) |
| Class 55 | 35 to < 50 PCF | Bricks, tiles, heavy automotive engines, dense hardware | Very Low |
| Class 60 | 30 to < 35 PCF | Car batteries, canned goods, heavy auto parts | Low |
| Class 65 | 22.5 to < 30 PCF | Bottled beverages, books, ceramic tiles, heavy tools | Moderate-Low |
| Class 70 | 15 to < 22.5 PCF | Car engines, machine parts, packed food items | Standard Base Rate |
| Class 85 | 12 to < 15 PCF | Cast iron sinks, tires, packed textiles, printed media | Standard-High |
| Class 92.5 | 10 to < 12 PCF | Computers, electronics, office equipment, pumps | Elevated |
| Class 100 | 8 to < 10 PCF | Wine cases, framed art, small appliances, outboard motors | High |
| Class 125 | 6 to < 8 PCF | Household appliances, lamps, bookcases, assembled furniture | Very High |
| Class 175 | 4 to < 6 PCF | Mattresses, sheet metal parts, clothing in boxes, paddles | Premium |
| Class 250 | 2 to < 4 PCF | Bamboo furniture, plastic tubing, solar panels, lampshades | Extreme Premium |
| Class 300 | 1 to < 2 PCF | Light foam insulation, deer antlers, empty plastic bottles | Ultra Premium |
| Class 400 | Less than 1 PCF | Ping pong balls, styrofoam beads, uncompressed feathers | Maximum Rate (Highest) |
Classes 77.5, 110, 150, 200 and 500 left the density scale in Docket 2025-1. They remain valid NMFC classes where a commodity-specific listing assigns them on handling, stowability or liability grounds, so a shipment can still be rated Class 500 — just never on density alone.