How is freight class calculated?

For most shipments, density determines class. Measure length, width, and height (in inches), divide by 1,728 to get cubic feet, then divide weight (lbs) by volume. Match the result to the NMFC density scale. For commodity-specific items, use ClassIT+ to find the correct NMFC item number.

What density ranges correspond to which classes?

The current NMFC density scale (13-subprovision, effective July 19, 2025) maps densities to classes. See the table above. For example, 50 lbs/cu ft or greater is class 50; 1 to less than 2 lbs/cu ft is class 400.

When should I recalculate my freight class?

Recalculate every time the shipment’s dimensions, weight, packaging, or contents change. Even small differences in pallet size or packing materials can shift density into a different class. For LTL shipments, recalculation avoids reclassification fees.

What are common mistakes when determining freight class?

Using approximated dimensions, forgetting packaging weight, mixing unit systems, and assuming the class stays the same for different products. Another frequent error: using the old 18-class density scale instead of the current 13-subprovision scale. Always verify with the NMFC or ClassIT+.

What is the difference between NMFC and freight class?

The NMFC is the full classification system published by the NMFTA. It includes thousands of specific commodity codes (NMFC numbers) and their corresponding classes. The freight class (50-500) is the numeric grouping within the NMFC. The NMFC is the rulebook; the freight class is the number you assign from that rulebook.

How does freight class affect shipping cost?

Shipping cost is calculated as: (weight in CWT) × (CWT rate) × class factor. Lower classes (dense items) have lower class factors and lower rates. Higher classes (light, bulky items) have higher class factors and higher rates. Accessorial charges and discounts also apply.

What Is Freight Class? NMFC Classes Explained

Q: What is freight class?

Freight class is a numeric code (50-500) assigned to LTL shipments that, with weight, sets the freight rate. The NMFC defines it based on density, stowability, handling, and liability.

What Is Freight Class?

Understanding what is freight class is essential: it is a numeric code between 50 and 500 that, combined with weight, determines the rate for less-than-truckload (LTL) shipments. The National Motor Freight Classification (NMFC) defines this class based on four characteristics: density, stowability, handling, and liability. Carriers use the class to set a price per hundredweight (CWT). A lower class means a lower rate, and a higher class means a higher rate. Getting the class wrong triggers reclassification fees and surprise bills.

Who Publishes The NMFC And Who Uses It

The National Motor Freight Traffic Association (NMFTA) publishes and maintains the NMFC. It is a non-profit that updates the classification through dockets and decisions. The NMFTA website (nmfta.org) hosts the official NMFC and the NMFTA Help Center "NMFC Classification FAQs" and the NMFTA "About the NMFC" page explain the system. LTL carriers, such as Old Dominion Freight Line (ODFL) and C.H. Robinson, use the NMFC class to calculate rates. They also publish their own rules tariffs that define accessorial charges, dimension rounding, and reweigh fees.

The Four Transportation Characteristics: Density, Stowability, Handling, Liability

Calculate Density First

Density is the primary factor. Calculate it as weight (lbs) divided by volume (cubic feet). Volume is length × width × height (in inches), divided by 1,728. For example, a pallet measuring 48 × 40 × 36 inches has a volume of 40 cubic feet. If it weighs 500 pounds, its density is 12.5 lbs/cu ft.

Stowability, Handling And Liability

Stowability measures how easily a handling unit fits in a trailer. Odd shapes or items that cannot be stacked increase the class. Handling covers the ease of loading and unloading, items requiring team delivery or special equipment get a higher class. Liability reflects the risk of damage or theft; high-value electronics or fragile goods carry a higher class.

The NMFC assigns a class per commodity item number. The density scale is a guideline for items without a specific item number. Always check ClassIT+, the NMFTA’s online classification tool, for the current NMFC item.

Density-Based vs. Commodity-Specific Items

Most shipments fall into one of two categories. Density-based items rely on the density scale to set the class. The current NMFC density scale (13-subprovision scale, effective July 19, 2025) replaced the old 18-class guideline. The 13 subprovisions are:

Less than 1 lb/cu ft
1 to less than 2 lbs/cu ft
2 to less than 4 lbs/cu ft
4 to less than 6 lbs/cu ft
6 to less than 8 lbs/cu ft
8 to less than 10 lbs/cu ft
10 to less than 12 lbs/cu ft
12 to less than 15 lbs/cu ft
15 to less than 22.5 lbs/cu ft
22.5 to less than 30 lbs/cu ft
30 to less than 35 lbs/cu ft
35 to less than 50 lbs/cu ft
50 lbs/cu ft or greater

Commodity-specific items have their own NMFC item number and class that override the density scale. For example, a specific type of machinery or hazardous material may have a class set by its characteristics. Use ClassIT+ to find the correct item number.

How Class Affects Your Rate

LTL pricing starts with a base rate from the CzarLite tariff, which provides a CWT rate for each class and weight bracket. The carrier applies a discount percentage off that base rate. The final charge is: (CWT rate × weight in CWT) × discount, plus accessorial charges. A lower class (e.g., 50) gives a lower CWT rate and a lower total cost. A higher class (e.g., 300) gives a higher rate.

Accessorial charges include liftgate, residential delivery, inside delivery, and reweigh/inspection fees. Each carrier lists its charges in its rules tariff. Dimension rounding, how the carrier rounds length, width, and height, also affects density. Check the carrier’s rules tariff for their rounding rule.

Failure to declare the correct class can lead to a reclass. The carrier may reweigh or inspect the shipment per NMFC Item 360 and charge a reweigh/inspection fee. The fee amount varies by carrier and is published in their rules tariff.

Freight Class Definition: What The NMFC Scale Looks Like

The NMFC density scale maps each density range to a class. Use the table below for the 13-subprovision scale. This is the current rule, effective July 19, 2025, from the NMFTA Docket 2025-1 final decision.

NMFC Density Scale (13-Subprovision, Effective July 19, 2025)

Density Range (lbs/cu ft)	NMFC Class
Less than 1	500
1 to less than 2	400
2 to less than 4	300
4 to less than 6	250
6 to less than 8	175
8 to less than 10	150
10 to less than 12	100
12 to less than 15	100
15 to less than 22.5	85
22.5 to less than 30	70
30 to less than 35	65
35 to less than 50	55
50 or greater	50

Who This Suits And Who Should Skip

Anyone who must classify their own LTL freight: small-business shippers getting accurate quotes, e-commerce staff packing pallets, logistics coordinators verifying carrier codes, and freight brokers quoting rates. If you handle full-truckload (FTL) or parcel shipments, or if you need international ocean/air classification under the Harmonized System (HS), use a TL rate guide, a parcel carrier’s website, or the HS tariff.

The most common failure: using the old 18-class density scale from pre-2025 guides or calculators. That scale is no longer authoritative. Always use the 13-subprovision scale from the NMFTA Docket 2025-1 final decision. If your calculator shows an 18-class table, find one that uses the current NMFC.