How to Calculate Freight Density for LTL, Step by Step

Freight density is the weight of a shipment divided by the space it takes up, measured in pounds per cubic foot (lb/ft³, often written pcf). In less-than-truckload (LTL) shipping, density is the main factor in freight class, and class is a big part of what you pay. Not every item goes by density, though. Commodities with handling, stowability or liability issues keep their own class under their National Motor Freight Classification (NMFC) item number. The freight class chart shows how the classes line up.

It pays to work out density yourself before you request a quote. If a carrier thinks the information on your bill of lading (BOL) is incomplete or inaccurate, it can reweigh the freight, inspect it and check your density calculation. The math itself is one line:

Density (lb/ft³) = total weight (lb) ÷ total volume (ft³)

The hard part is feeding it the right numbers.

How to calculate freight density in five steps#

Step 1: Measure the handling unit, not the product

Measure the finished handling unit (each pallet, crate or loose piece) exactly as you’ll tender it: the pallet, the freight, any overhang and anything that sticks up on top, including stretch wrap that bulges above the load. Box dimensions from a spec sheet don’t count on their own.

Take the greatest straight-line length, width and height in inches. Don’t run a tape around the load; circumference isn’t what carriers measure. Height runs from the floor to the highest point. Overhang goes into the dimension too: a pallet that’s 40 in wide with 2 in hanging over each side measures 44 in (40 + 2 × 2).

Step 2: Convert to cubic feet

Multiply length × width × height in inches, then divide by 1,728, the number of cubic inches in a cubic foot (12 × 12 × 12).

Cubic feet = L × W × H (in) ÷ 1,728

Step 3: Weigh the unit as tendered

Use the gross weight of the handling unit as you hand it to the carrier: freight plus packaging plus pallet. A standard 48 × 40 in pallet typically weighs about 37 lb (17 kg), and its deck adds roughly 5.7 in to the height. Both belong in the calculation. For other footprints, see standard pallet sizes.

Step 4: Divide weight by cubic feet

Divide total pounds by total cubic feet. For a single pallet, you’re done.

With several handling units on one shipment, the NMFC rule (Item 110, Sec. 8(d)) is to figure density for each handling unit separately. The exception: when the shipping papers show only a total weight, density is total weight ÷ total cubic feet.

Whichever applies, don’t average the per-unit densities. A combined density is weighted by volume (total lb ÷ total ft³), so a simple average of the individual figures gives a different number. The example below shows how far apart they can be.

Step 5: Find the class on the density scale

Look up your result on the NMFC density scale, the standard table that assigns a class to each density range. It has 13 density ranges, known as subs, running from class 50 to class 400. Each range includes its lower bound and stops just short of the upper one, so exactly 15 lb/ft³ is class 70. Carriers print the same table in their own tariffs; ODFL’s is in its 100-Q tariff, Item 640-3. (The full freight class system has 18 classes, from 50 to 500; the density scale uses 50 through 400.)

The freight class calculator handles steps 2 through 5 for you. It uses the same scale, but it can’t know whether your commodity has an item-specific class, and it doesn’t apply the per-unit rule or the carrier’s non-stackable height rule (both covered below). Treat its answer as a density-based estimate.

Where the rules come from: the classification itself is the NMFC, published by the NMFTA. Inspection fees and extra measuring rules sit in each carrier’s rules tariff (its published terms and accessorial rules).

Worked example: two pallets on one bill of lading#

Two standard pallets ship together. One is short and heavy, the other tall and light.

Pallet 1 is 99,840 cubic inches and pallet 2 is 124,800, for a total of 224,640 cubic inches, or 130.0 ft³. Combined density: 1,050 ÷ 130.0 = 8.08 lb/ft³, class 100 (8 to under 10).

Taken one at a time, the pallets tell a different story. Pallet 1 comes to 11.08 lb/ft³, class 92.5 (10 to under 12). Pallet 2 comes to 5.68 lb/ft³, class 175 (4 to under 6). Average those two and you get 8.38, which matches neither method. The combined figure is lower because the light pallet takes up more of the space.

So which result applies? Per unit is the NMFC starting point. The single 8.08 lb/ft³ class applies when the bill of lading shows only a total weight, or when the carrier can’t match weights to pallets. ODFL’s Item 640 spells this out: list each pallet’s weight on the BOL and label each pallet so the carrier can check it, and each one rates at its own density. If the weights can’t be matched to the pallets, the carrier may rate the whole shipment on overall density instead. With per-pallet weights and labels, this shipment could move as class 92.5 and class 175.

The calculator uses the combined method. It rolls every row into one density and one class and doesn’t show results per row. Open this example in the calculator and you’ll see 130.0 ft³, 1,050 lb, 8.1 lb/ft³ and class 100.

Where density calculations go wrong#

Measuring the boxes instead of the pallet

Say a spec sheet built from box dimensions works out to 12 lb/ft³, which is class 85. Measure the finished pallet, with its deck, the empty space above the top tier and the wrap bulge, and the same freight might come in at 9.4 lb/ft³. That’s class 100.

Overhang

Widen a 48 × 40 in pallet load from 40 in to 44 in and the footprint grows by 10% (2,112 ÷ 1,920 = 1.10). Density shrinks to 40/44 of what it was, about 9.1% lower. Carrier packing guidelines also say freight shouldn’t hang past the pallet edge, so overhang raises the risk of damage and weakens your position if you file a claim. The usual fix is a different box layout; see how many boxes fit on a pallet.

Rounding measurements down

The rules tariffs we checked (ODFL 100-Q, Saia 170-D and Estes) don’t set a rule for rounding inches, so don’t count on any particular one. The safe habit is simple: never round a measurement down on a quote. If you’re between inches, use the higher number.

Non-stackable freight

Some freight is non-stackable, meaning nothing may be placed on top of it, because of the commodity, the packaging or a pyramid or rounded top, or because the BOL says so. For units like these, ODFL (Item 490-2) and Saia (Item 111-2e) may rate the unit at a height of at least 96 in.

Here’s what that does to a 48 × 40 in pallet weighing 500 lb. Measured at its actual 48 in, it’s 53.33 ft³, 9.375 lb/ft³ and class 100. Rated at 96 in, it becomes 106.67 ft³, 4.69 lb/ft³ and class 175.

ODFL has two related rules. Freight 70 in wide or more can be rated as 96 in wide (Item 490-4). And when individual pieces can’t reasonably be measured for cube, volume is taken as linear feet × actual height (minimum 96 in) × 96 in width (Item 490-3).

Low-density rules

Very light, bulky shipments can also run into a low-density minimum charge, which in effect sets a floor on the weight you’re billed for. Under ODFL Item 610-1, a shipment of 750 ft³ or more that averages under 6 lb/ft³ is billed as if it weighed 6 lb per cubic foot, at class 125 rates. Other carriers set their own thresholds.

Several shipments on the same day

Splitting a load across several bills of lading doesn’t necessarily reset the math. Under ODFL Item 366, when the same shipper sends several shipments on the same day from the same place to the same consignee at one location, the carrier may treat them as a single shipment. Saia reserves the right to combine shipments to the same consignee on the same day (Item 360-70), and Estes counts them as one shipment when it checks cubic capacity (Item 615, Application 3).

Packing list weights

A supplier’s packing list may leave out the weight of the boxes, dunnage (loose material used to brace and protect cargo), wrap or pallet. Weigh the finished unit, or add the packaging weight yourself.

Carrier scales and weight corrections

Carriers weigh freight on certified scales, meaning scales approved for commercial weighing. Estes (Item 992-1) uses NTEP-certified, legal-for-trade scales and may weigh freight without notice. ODFL (Item 367-5) states that its portable electronic scales are accurate to within 1%.

A wrong weight costs money even when the class doesn’t change. At ODFL, a weight increase of 20 lb or more brings a $25 charge per shipment, and the freight charges, fuel surcharge and accessorial charges are recalculated on the new weight.

What actually improves density

Packaging design. Cut empty space, pack tighter, keep wrap to a minimum and build the load lower. Those changes raise density honestly, and they hold up when the carrier measures.

How a reclass ends up on your invoice#

Carriers can reweigh, inspect and check the density calculation on any shipment where they believe the BOL information is incomplete or inaccurate (ODFL Item 367-1). This is the weigh and inspect process, which shows up on invoices as a reweigh and reclassification. The terminal reweighs, remeasures and inspects the freight. If the results don’t match the BOL, the shipment is rerated at the measured class and a fee from the rules tariff is added. The fees vary by carrier:

• ODFL (Item 367-2): $25 per shipment when inspection results in a reclass, plus recalculated freight charges, fuel surcharge and accessorial charges.
• Saia (Item 850): $44 per shipment when an inspection or reweigh adjusts the line haul charges, which cover the main terminal-to-terminal move.
• Estes: $20 for a commodity inspection (Item 993-10) and $20 for weighing (Item 993).

Example: class 85 on paper, class 100 at the terminal

This case is hypothetical. A housewares importer ships three pallets of storage bins. The BOL density comes from the box dimensions on the factory spec sheet: 12.3 lb/ft³, class 85 (12 to under 15). At the transfer terminal the pallets measure taller, because of the pallet deck and the wrap bulge on top, and wider, because the wrap bulges about 1 in on each side. Measured density: 9.6 lb/ft³, class 100 (8 to under 10).

That’s two steps on the density scale, from 85 to 92.5 to 100, and each step up in class number is a step up in rate. For the same weight, the measured volume is about 28% larger (12.3 ÷ 9.6 = 1.281).

The corrected invoice then carries:

1. Every pound rerated at class 100.
2. The carrier’s reweigh and reclassification fee from its rules tariff, $25 per shipment at ODFL.

If the mismatch repeats shipment after shipment, the extra cost keeps adding up, and a record of reclasses can also work against you when your contract discount comes up for renegotiation. The fix in a case like this: measure five finished pallets, average their actual height and footprint, and update the dimensions in your BOL template.

Drums, metric specs, mixed-class loads and breakpoints#

Round and irregular freight

Measure the rectangular box that fully encloses the item: greatest length × greatest width × greatest height. For a 55-gallon drum, that’s diameter × diameter × height. The empty corners around a round item count as volume, so density comes out lower than it looks.

Specs in cm and kg

When the factory sends dimensions in centimeters and weight in kilograms, convert first: cm to inches (1 in = 2.54 cm) and kg to pounds (1 lb = 0.45359237 kg). Then use the standard formula. Alternatively, work out density in kg/m³ and convert the result at 1 lb/ft³ = 16.01846 kg/m³ (about 16.02). That makes 150 kg/m³ about 9.36 lb/ft³, or roughly 9.4. What you shouldn’t do is mix unit systems partway through the calculation.

Parcel and air carriers use the same principle with dimensional weight (called volumetric weight outside the US): you pay for the outside dimensions, even though the divisors differ. See volumetric weight explained.

Mixed-class shipments

A mixed-class shipment is one bill of lading covering items that rate at different classes. Show the pieces and weight for each class separately on the BOL. If the carrier finds the BOL inaccurate, it can rate the whole shipment on overall density (ODFL Item 640-2). And when the load includes items that aren’t density-rated, items with handling, stowability or liability issues, or hazardous materials, Estes (Item 645) may rate everything at the class of the highest-class item.

Breakpoints

Each band includes its lower bound. Exactly 15.0 lb/ft³ is class 70; 14.9 is class 85.

Freight sitting just above a breakpoint doesn’t have much room. At 15.1 lb/ft³, class 70 with only 0.67% to spare, a 48 in tall unit that picks up 1 in of height falls to 15.1 × 48 ÷ 49 = 14.79 lb/ft³ and moves to class 85. If you’re within a few percent of a breakpoint, build in real margin by lowering the stack or wrapping tighter, or quote at the higher class number on the other side of the line.

Freight density to class: quick reference#

All 13 bands are in the freight class chart. The classification itself comes from the NMFC, published by the NMFTA. Inspection fees and measuring rules come from each carrier’s rules tariff; ODFL, Saia and Estes, among others, publish theirs.