The 4 Factors That Determine Freight Class, Explained

Every NMFC freight class traces back to four transportation characteristics: density, stowability, handling, and liability. Together they answer one question from the carrier's side of the dock — how expensive is this freight to move, per pound, compared to everything else on the trailer?

Since the NMFTA's 2025 restructure, density does most of the work for most freight, but the other three factors are why two shipments with identical density can still carry different classes. Understanding all four tells you when the density calculator is the whole answer and when your commodity's NMFC item is going to override it.

Density: the dominant factor

Density is weight per volume — pounds per cubic foot (PCF), computed from the shipment as it actually ships: total weight including pallet and packaging, divided by total cube measured at the extreme points. It matters because an LTL trailer sells out by space as often as by weight; freight that's light for its size consumes the carrier's real constraint. Low density, high class, high price. Dense freight subsidizes nothing and rates cheap.

With the NMFC changes effective July 2025, commodities without significant issues on the other three factors moved to straight density-based classing on a 13-tier scale running from class 50 (50+ PCF) up to class 400 (under 1 PCF). For typical palletized general freight, this makes density not just the first factor but effectively the only one — and it makes your class configuration-dependent: repack the same product taller or looser and the class legitimately changes.

Tip Density is also the only factor you can engineer week to week. You can't make your product less fragile by Thursday, but you can take four inches of air out of the packaging and cross a class break.

Stowability: how well it shares a trailer

Stowability asks whether your freight loads efficiently alongside other freight. A cube-shaped, stackable pallet is ideal: it tessellates, other freight rides on top, no space dies around it. Freight scores poorly on stowability when it protrudes, can't be stacked or have anything stacked on it, has excessive length or weird geometry, or can't legally travel next to other goods — hazardous materials with segregation requirements being the classic case.

Overlength items (pipe, lumber, rolled carpet) that monopolize floor positions.
Non-stackable or top-load-only freight that kills the vertical space above it.
Odd shapes and overhang that leave unusable voids around the unit.
Regulatory incompatibilities that force the carrier to isolate the freight.

Poor stowability raises class because the carrier is effectively selling you the dead space your freight creates, not just the space it occupies.

Handling: what it takes to move it through terminals

LTL freight is cross-docked — loaded, unloaded, and reloaded at terminals between pickup and delivery. Handling measures how much care and effort that takes. A shrink-wrapped pallet that a forklift moves in one pass is the baseline. Class pressure comes from anything that slows the dock down or raises the odds of damage in transit handling:

Fragile freight that needs careful placement or can't tolerate normal dock handling.
Unpalletized, loose, or floor-loaded pieces that require hand work.
Extreme weight or dimensions needing special equipment.
Protruding parts, poor packaging, or unstable units likely to shift or snag.

Handling problems are often really packaging problems — the same commodity in a proper crate or on a well-built pallet can present none of the issues its loose-shipped version does, which is one reason NMFC items sometimes specify packaging requirements.

Liability: the risk the carrier is absorbing

Liability covers the carrier's exposure while your freight is in their care: value per pound, susceptibility to damage, theft attractiveness, perishability, and the potential to damage adjacent freight (leaking, combustible, odor-producing goods). High-value electronics, fragile glass, and hazardous materials all carry liability pressure regardless of how dense or stackable they are.

Liability is also where released-value and declared-value provisions interact with class — some NMFC items tie classification or carrier acceptance to declared value per pound. If your freight is unusually valuable for its weight, read the item language carefully and check your carrier's liability terms; class is only part of that conversation.

How the four factors combine after the 2025 changes

Think of it as a default with overrides. Density sets the class for the broad middle of general freight — that's what the 2025 restructure formalized by moving thousands of commodity listings onto the density scale. Stowability, handling, and liability act as modifiers: when a commodity has a genuine issue on one of those dimensions, its NMFC item can assign a class different from what raw density would suggest, or attach conditions (packaging, declared value) to the classification.

Ask first: does this freight have any special characteristic — fragile, hazardous, very long, non-stackable, high value per pound? If clearly no, density is your class; measure and compute it.
If possibly yes, look up the commodity's NMFC item (via NMFTA's ClassIT or your carrier) and read whether it's density-rated or carries its own class and conditions.
Either way, measure the real shipment — even for items classed on other factors, accurate dims and weight on the BOL prevent reweigh and inspection surprises.
Document what you found: the item number, the class logic, and a dated worksheet. When a carrier's correction disagrees, your paper is the counterargument.

Tip If you remember one thing: density is measurable, and the other three factors are mostly properties of your commodity that change rarely. Measure density every time the configuration changes; revisit the other three when the product, packaging, or value changes.

Common questions

Do carriers score each factor separately?

Not as four separate numbers on your quote. The factors are baked into the NMFC classification itself — the NMFTA weighs them when assigning classes to commodity listings. Your job is knowing which regime your commodity falls under: density-rated (you compute it) or item-specific (you look it up).

Can good packaging lower my class?

It can, two ways. Directly: denser packaging raises PCF and can cross a density break. Indirectly: proper crating or palletizing can resolve the handling and stowability issues that push some commodities off the pure density scale. It can also cut damage claims, which is worth more than class over time.

My freight is dense but fragile. Which factor wins?

Check the NMFC item. Density-based classing applies to freight without significant handling, stowability, or liability issues — a genuinely fragile or high-liability commodity can be classed on those characteristics even at high density. The item language, not intuition, settles it.

Did the 2025 changes eliminate the other three factors?

No — they reweighted the system toward density for general freight and consolidated thousands of listings, but stowability, handling, and liability remain part of the classification framework and still drive class for commodities with real issues on those dimensions. Verify your specific item against the current NMFC rather than assuming either way.