NMFC
The National Motor Freight Classification is the classification system that assigns less-than-truckload freight to a class. Its classes run from 50 to 500, and density is only one of the inputs that decide which one applies. The system also carries rules, and unique identifiers for freight whose characteristics mean a plain density band does not fit it.
Where density fits in the NMFC
The NMFC class system runs from class 50 to 500; the density scale used on this site can only produce classes from 400 down to 50.
FedEx Freight lists density, stowability, handling and liability as the transportation characteristics a class is calculated from, so density is one input among several.
Density-based entries are published against a rule as well as a density, which is why they read Subject to Item 170 and having a density in pounds per cubic foot of.
Frequently asked
Is density the only thing that decides an NMFC class?
No. FedEx Freight lists density, stowability, handling and liability as the transportation characteristics a class is calculated from, and NMFTA states that unusual or significant handling, stowability or liability characteristics may be a contributing factor in the assignment of classes.
Why does this site say the density scale stops at class 400 when classes go up to 500?
They are two different ranges. The NMFC class system runs from 50 to 500, while the 13-subprovision density scale can only produce classes from 400 down to 50. A class above 400 does not come from this density scale.