In this article, learn about:
Density in LTL shipping
How to calculate density
Freight classification by density
Minimum density and cubing out regulations
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What is Density in LTL Shipping?
Calculating density is the foundational principle for understanding LTL logistics. Density in cubic square feet is the main metric for determining freight class. Freight classification is essential for logistics companies to understand how to load their trucks.
To understand your product’s density and freight class, follow this simple three-step process.
Related Reading: What is an NMFC Number?
Step 1: Calculate Cubic Footage
In order to calculate the cubic footage of an item, start by measuring its dimensions: Length, Width, and Height. These numbers, multiplied and divided by 1,728 will give you the cubic footage because 1 cubic foot contains 1,728 cubic inches (i.e. 12 x 12 x 12).
Step 2: Calculate Density
Getting an accurate understanding of density is essential for transportation and logistics purposes. In logistics, Density = Total Weight / Cubic Footage.
Step 3: Calculate Freight Class by Density
The National Motor Freight Traffic Association (NMFTA) defines freight class as “a classification used by shipping companies for less-than-container load freight shipments.” Universal freight class codification helps all LTL carriers on the same page.
These class numbers range from 50-500, with the easier to handle products typically falling closer to a classification of 50 and the harder to handle products getting closer to 500.
Freight Class Chart with Examples
There are many examples of what sorts of products fall where along the spectrum from 50-500:
Freight Class Code | Type of Freight | Weight Per Ft³ |
50 | Heavy industrial machinery, steel coils | 50+ lbs. |
55 | Concrete blocks, ceramic tiles, roofing materials | 35–50 lbs. |
60 | Engine blocks, car suspensions | 30–35 lbs. |
65 | Bulk canned goods, packaged beverages | 22.5–30 lbs. |
70 | Car tires, air compressors, packaged grains | 15–22.5 lbs. |
77.5 | Bathroom sinks, vinyl flooring rolls | 13.5–15 lbs. |
85 | Cast iron bathtubs, metal cabinets | 12–13.5 lbs. |
92.5 | Refrigerators, gaming consoles, washing machines | 10.5–12 lbs. |
100 | Plastic containers, patio umbrellas, wooden crates | 9–10.5 lbs. |
110 | Office desks, picture frames, wooden shelves | 8–9 lbs. |
125 | Microwaves, coffee makers, air fryers | 7–8 lbs. |
150 | Aluminum sheets, book collections | 6–7 lbs. |
175 | Clothing racks, leather chairs, foam furniture | 5–6 lbs. |
200 | Flat-pack furniture, packaged ceiling fans | 4–5 lbs. |
250 | Mattress toppers, LED TVs, bamboo panels | 3–4 lbs. |
300 | Assembled bookshelves, wooden tables | 2–3 lbs. |
400 | Foam insulation panels, plastic deer statues | 1–2 lbs. |
500 | Packing peanuts, cotton balls | <1 lb. |
What’s most important is to note the relationship between freight class code number (i.e. 50-500) and the density (i.e. Weight per ft³), which are relatively universal principles. The Type of Freight column in the middle contains our custom examples.
See also the FedEx Freight Class Calculator for the examples that they pick for each of the freight classes.
Freight Classification Examples
The examples of bricks for a freight classification of 55 and ping pong balls for a classification of 500 are helpful for illustrating the main goal of freight classification as a whole.
Ping pong balls, on first thought, do not seem like something that would be challenging to ship in a truck. But they are easily damaged (fragile), lightweight, and spherical. A truck designed to carry 80,000 pounds of freight that is half full of ping pong balls, will have to pair the ping pong balls with an item of a much lower classification in order to travel safely.
If an item is 13 lbs./cubic foot, then it would have a freight class code of 85.
Each of these codes applies to the whole spectrum of the density in the far right column of the table. So, anything up to 13.5 lbs./cubic foot still counts as an 85, and anything that is 12-10.5 lbs./cubic feet is a code 92.5.
What is Minimum Density/Cubic Capacity in LTL Shipping?
In logistics, cubing out is when a shipment reaches its volumetric or dimensional capacity. An ideal LTL logistics company can make the most out of any given shipment by pairing it with a complementary freight class, shipping size, or destination (or all three!).
This volumetric or dimensional capacity is also referred to as the cubic capacity. Cubic capacity is relevant for all forms of truck shipping, but it is most relevant for LTL shipping because of the technical complications involved in shipping below the FL threshold.
Calculating LTL Minimum Cubic Capacity
The 750 & 6 Rule is a helpful, industry-wide standard for thinking about the floor of cubic capacity. For most LTL shipments, you want a floor of 750 cubic feet per shipment, in which each cubic foot is at least 6 pounds per cubic foot.
There are a lot of exceptions to this rule, and some shippers specialize in shipments below that floor, but for large shipping quantities, the 750 & 6 Rule is the standard. Although the 750 & 6 Rule is fairly standard, it is most relevant to LTL shippers who deal with a variety of cubic density codes, usually across a large number of customers.
Linear Foot Rules
Linear foot rules are a less common form of cubic rules like the 750 & 6 rule that are focused more on regulations around maximum length. It is still used for shipments of items of significant length.
When shipments take up 10 linear feet or more of space in a trailer, they can be hit with much larger fees, usually accessorial fees, reclassification fees, and/or elevated rates. These are sometimes similar to over cube charges or other such fees like those featured in the section below.
Overlength, Extreme Length, and Over Dimension Rules
Just as it sounds, overlength, extreme length, and over dimension rules are simply measures and regulations put in place, usually by the logistics/shipping company itself, to make sure that they are shipping efficiently.
For many companies there is a hard cut off at 96 inches in any dimension. This length will usually incur an additional fee on top of regular shipping costs.
For example, UPS will charge an additional $90/shipment for shipments containing one or more articles that are equal to or greater than 8 feet and less than 12 feet in one dimension. There are subsequent fees that increase based on the size of the items that exceed the maximum lengths.
Watching Out for Reclassification Charges
Once an NMFC classification has been determined for an item, that is not necessarily the end of the story. Some shippers will charge reclassification fees to suppliers if the original classification appears to have become inaccurate.
Related Reading: All Things LTL
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