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 established by the National Motor Freight Traffic Association (NMFTA). It categorizes commodities into 18 distinct freight classes ranging 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.
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 ($D \times D \times H$), 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.
What is "Bump Weight" & How Does It Save Money?
Under NMFC Item 171 rules, shippers are legally allowed to "bump" a shipment to a lower freight class by declaring artificial extra weight on the Bill of Lading (BOL). If adding a few hypothetical pounds increases your overall PCF past the threshold into a lower class, the lower class freight rate can reduce your total invoice cost—even though you pay for slightly more weight!
Our Class Bump Advisor automatically computes the exact minimum weight needed to trigger the next class drop.
Official NMFC 18-Tier Freight Class Table
| 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 77.5 | 13.5 to < 15 PCF | Tires, snow globes, packed textiles, printed media | Standard |
| Class 85 | 12 to < 13.5 PCF | Cast iron sinks, packaged hardware, leather goods | Standard-High |
| Class 92.5 | 10 to < 12 PCF | Computers, electronics, office equipment, pumps | Moderate-High |
| Class 100 | 9 to < 10 PCF | Wine cases, boat covers, framed art, wine glasses | High |
| Class 110 | 8 to < 9 PCF | Framed canvas, small appliances, outboard motors | High |
| Class 125 | 7 to < 8 PCF | Household appliances, lamps, small furniture | Very High |
| Class 150 | 6 to < 7 PCF | Bookcases, assembled furniture, luggage | Premium |
| Class 175 | 5 to < 6 PCF | Paddles, clothing in boxes, light lamps | Premium |
| Class 200 | 4 to < 5 PCF | Sheet metal parts, mattresses, light aluminum fabrications | Heavy Premium |
| Class 250 | 3 to < 4 PCF | Bamboo furniture, plastic tubing, solar panels | Extreme Premium |
| Class 300 | 2 to < 3 PCF | Model airplanes, light kayaks, unpacked lampshades | Ultra Premium |
| Class 400 | 1 to < 2 PCF | Light foam insulation, deer antlers, empty plastic bottles | Near-Maximum |
| Class 500 | Less than 1 PCF | Ping pong balls, styrofoam beads, uncompressed feathers | Maximum Rate (Highest) |