Freight Class Guide: How NMFC Codes Work and Why They Determine Your LTL Rate

If you ship LTL (less-than-truckload) freight, freight class determines a significant portion of what you pay. Misclassify your freight — whether by accident or by wishful thinking — and you’re either overpaying consistently or getting slapped with reclassification fees after the fact. Neither is good.

Freight class is not a simple lookup. It involves four factors — density, stowability, handling, and liability — and the National Motor Freight Classification (NMFC) system that governs it was designed for an era before automated shipping platforms and modern density-based pricing. Understanding how it works gives you a real advantage in negotiating freight rates and avoiding expensive errors.

What Is Freight Class?

Freight class is a standardized system for categorizing LTL shipments by the type and characteristics of the freight. It was created by the National Motor Freight Traffic Association (NMFTA) and published as the NMFC — the National Motor Freight Classification.

There are 18 freight classes, ranging from Class 50 (densest, cheapest to ship) to Class 500 (lightest/most difficult, most expensive to ship).

Class	Density (lbs per cubic foot)	Examples
50	50+	Bricks, steel, cement
55	35-50	Hardwood floors, auto parts
60	30-35	Beverages, tiles
65	22.5-30	Rolled steel, printed materials
70	15-22.5	Car engines, tools
77.5	13.5-15	Refrigerators
85	12-13.5	Crated appliances
92.5	10.5-12	Computers
100	9-10.5	Wine cases, caskets
110	8-9	Furniture
125	7-8	Auto glass
150	6-7	Mattresses, copiers
175	5-6	Electronic displays
200	4-5	Aircraft parts, machinery
250	3-4	Bamboo furniture
300	2-3	Wood cabinets
400	1-2	Deer antlers (historical NMFC item)
500	Less than 1	Gold dust, ping pong balls

Higher class = higher LTL rate per hundredweight (CWT). Class 500 freight can cost 10x or more per pound than Class 50.

The Four Factors That Determine Freight Class

Freight class is not based solely on density, although density is the primary driver. The NMFC system considers four characteristics:

1. Density

Density is calculated as pounds per cubic foot: weight divided by volume. Dense freight is cheaper to ship because carriers can stack and fill trailers efficiently — they can load more weight without running out of cube. Light, bulky freight wastes trailer space.

Calculating density:

Measure the shipment dimensions in inches (including packaging, pallet, and all protrusions)
Calculate volume: (length × width × height) / 1,728 = cubic feet
Calculate density: weight (lbs) / cubic feet

Example: A pallet that is 48” × 40” × 36” and weighs 200 lbs:

Volume: (48 × 40 × 36) / 1,728 = 69,120 / 1,728 = 40 cubic feet
Density: 200 / 40 = 5 lbs per cubic foot → approximately Class 175-200

2. Stowability

Stowability refers to how easily the freight can be loaded and positioned alongside other freight. Irregular shapes, oversized items, hazardous materials that can’t be stacked with other freight, or items requiring special positioning reduce stowability and increase the class.

Freight that takes up disproportionate space in a trailer — wide, tall, or shaped in ways that prevent efficient stacking — gets a higher class even if the density calculation suggests a lower one.

3. Handling

Handling refers to the care required to move the freight through the LTL network. Standard palletized boxes score well on handling. Freight that requires special equipment (cranes, flatbeds, specialized lift gates), is fragile, contains liquids that could leak, or is hazardous requires more careful — and expensive — handling, resulting in a higher class.

4. Liability

Liability reflects the cargo’s susceptibility to damage and the carrier’s exposure. High-value freight (electronics, jewelry), perishable goods (fresh food, pharmaceuticals), or freight with high theft risk carries a higher class because the carrier’s liability exposure is greater.

How to Look Up Your NMFC Code

Every commodity shipped LTL should have an NMFC item number — a specific code in the NMFC directory that determines its class. You can look up NMFC codes through:

The ClassIT tool at ClassIT.com (subscription-based official NMFC lookup)
Your carrier’s online shipping calculator (many carriers have free classification tools)
Your 3PL or freight broker — if you use a freight broker, they should be able to provide the correct NMFC item number for your commodity
The NMFC directory (available for purchase from NMFTA)

When looking up codes, be specific. “Electronics” has many different NMFC codes depending on the specific product, how it’s packaged, and what it contains. Generalizing your freight to a broad category often leads to the wrong class.

Density-Based Pricing vs. NMFC Classes

Over the past decade, many carriers have moved toward density-based pricing (DBP) as an alternative or supplement to NMFC classification. Under DBP, freight class is determined entirely by calculated density — no NMFC lookup required.

Advantages of density-based pricing:

More predictable — you can calculate the rate before shipping
Eliminates disputes over commodity classification
Rewards shippers who package freight efficiently (higher density = lower class)

When it doesn’t apply:

Some commodities are specifically excluded from density-based pricing by carriers (hazmat, high-value items, items with specific liability concerns)
Carriers may apply DBP only for their own contracted rates, not tariff rates

Ask your carriers whether DBP is available for your freight and whether it results in lower rates than NMFC-based classification. For dense, regularly shipped commodities, DBP often produces more favorable rates.

Reclassification: What Happens When You Get It Wrong

Carriers inspect and weigh LTL shipments at various points in the transit process. If they determine that your freight class doesn’t match what you declared, they can reclassify it — and charge you the difference plus a reclassification penalty.

Reclassification fees are not trivial. A shipment declared as Class 65 that gets reclassified to Class 150 can double or triple the freight charge, plus the penalty fee. For high-volume shippers, systematic misclassification creates significant invoice reconciliation problems.

The most common reclassification causes:

Incorrect dimensions: Shipment is larger than declared, resulting in lower calculated density and higher class
Wrong NMFC item: Generic classification used instead of the specific commodity code
Packaging not matching declaration: Declared as “boxed” but shipped as loose or irregularly packaged

To minimize reclassification risk:

Measure shipments accurately, including all packaging and pallet height
Use the specific NMFC item number for your commodity, not a general category
Audit carrier invoices — if you’re seeing frequent reclassifications on the same commodity, your classification process has a systematic error
Work with a TMS with freight audit capability to identify reclassification patterns

Freight Class and Rate Negotiation

Freight class is one of the primary levers in freight rate negotiation. Shippers with consistently high freight class — light, bulky, or difficult-to-handle freight — face structural cost disadvantages that negotiation can only partially offset.

Packaging optimization: Reducing the dimensional size of packaging while maintaining protection increases density and lowers class. For Class 150+ freight, a packaging redesign that moves you to Class 125 can have more impact than any rate negotiation.

Commodity reclassification: If you believe your freight is being classified at too high a class, you can file a NMFC reclassification petition through the NMFTA. This is worth pursuing for high-volume shippers with legitimate arguments for a lower classification.

Negotiating class exceptions: Some carriers will negotiate class exceptions for high-volume shippers — agreeing to apply a lower class than the published NMFC for specific commodities in exchange for volume commitments. Document your freight profile (volumes, lanes, density calculations) before negotiation and make the business case for the exception.

Minimizing class 125+ freight in LTL: For consistent Class 150+ freight, evaluate whether FTL (full truckload), specialty carriers, or alternative modes are more cost-effective than LTL. Class-based LTL pricing penalizes light freight disproportionately.

Common Freight Class Mistakes

Using weight instead of density to estimate class. A 500 lb shipment could be Class 50 or Class 500 depending on its volume. Weight alone tells you nothing about class.

Ignoring pallet height. Shippers often measure product dimensions but forget to add pallet height (typically 5.5” for a standard pallet) to the height calculation. This understates volume and overestimates density — leading to a declared class that’s too low.

Using approximate dimensions. Carriers measure shipments. If your declared dimensions are significantly smaller than actual, you’ll be reclassified and penalized. Use accurate measurements, rounded up to the nearest inch.

Assuming the same class for all items. Many shippers apply one freight class across their entire product catalog to simplify logistics. This leads to overpaying on dense items and underpaying (and getting reclassified) on light items.

Not reviewing carrier invoices for reclassifications. Reclassification fees often appear as line items on freight invoices that shippers don’t scrutinize. A regular invoice audit identifies systematic classification errors before they become a significant cost.

Freight Class for International Shipments

Freight class is a US domestic LTL concept — it doesn’t apply to international ocean freight (which uses Harmonized System / HS codes for classification) or international air freight. For US import shipments that will move via LTL from port to destination, freight class applies from the US port or distribution center onward in the domestic LTL leg.

For imports, the commodity classification at customs (HS code) is separate from and independent of the NMFC classification for domestic LTL. Companies sometimes confuse the two — they’re different systems for different regulatory purposes.

If your imported products undergo any processing or repackaging at a US distribution center before LTL shipping, the NMFC classification applies to the processed, packaged product — not the raw import. Density and stowability after final packaging determine the domestic freight class.

Working with a TMS to Manage Freight Class

A Transportation Management System (TMS) with a built-in freight class calculator and carrier rating engine removes much of the manual work in freight classification:

Automated density calculation from shipment dimensions and weight
NMFC lookup integration to match commodity codes to your product catalog
Class override capability when products have negotiated class exceptions with specific carriers
Rate shopping across carriers using correct class for each, identifying the most cost-effective option
Invoice audit against rated class to automatically flag reclassifications from carriers

For shippers with diverse product catalogs and high LTL volume, TMS-managed classification is more accurate and less labor-intensive than manual processes. The reduction in reclassification fees often covers a significant portion of TMS cost.

Bottom Line

Freight class is a system that rewards shippers who understand it and penalizes those who don’t. Getting your NMFC classification right — using specific item numbers, measuring accurately, and understanding how density, stowability, handling, and liability interact — is the foundation of accurate LTL pricing.

Beyond accuracy, freight class is a negotiation lever. High-class freight is expensive by design; the response is either packaging optimization to increase density, volume-based class exceptions, or mode shifting for the highest-class commodities.

For shippers managing significant LTL volume, the combination of accurate classification, regular invoice auditing, and rate negotiation informed by your freight class profile is one of the highest-ROI activities in freight cost management.