How freight class works for something that is mostly air

A carrier is selling space and weight capacity at the same time, and a trailer runs out of one before the other depending on what is in it. Freight classification exists to price that.

The key input is density in pounds per cubic foot. Dense freight — steel, liquids, machinery — fills the weight allowance while leaving space. Light bulky freight does the opposite, and pays for the space it occupies.

Running the numbers on a tote

External dimensions of a 275 gallon composite IBC are about 48 by 40 by 46 inches. That is 88,320 cubic inches, or roughly 51 cubic feet. Tare weight is about 145 pounds.

145 divided by 51 is about 2.8 pounds per cubic foot. For comparison, a pallet of bagged cement runs well over 30. An empty IBC is, from a carrier's point of view, a very large box of nothing.

What this does to an LTL quote

Low-density freight lands in a high freight class, and high classes cost more per hundredweight. Four empty totes occupy four pallet positions and weigh less than 600 pounds, so you are paying for four positions of trailer space while contributing almost nothing to the weight the carrier is allowed to move.

There is no negotiating position that changes this. It is arithmetic about the shape of the object.

Where double stacking changes everything

Empty containers stack two or three high in a trailer, which effectively doubles or triples the density of the load and is why full-truckload economics on empties are so much better than LTL.

Fifty units floor loaded becomes up to eighty double stacked. The trailer costs the same. That is the entire reason the cost per unit collapses above about forty.

Full containers behave completely differently

Once there is liquid inside, the density goes from 2.8 to nearly 50 pounds per cubic foot, and the constraint flips instantly from space to weight. A trailer with a 44,000 pound payload allowance reaches it at around eighteen full 275s while there is still room for thirty more.

Which is why the two directions of a returnable programme are not symmetrical. Outbound, you are weight limited and half the trailer is empty. Inbound, you are space limited and the trailer is full of air. Anybody designing a loop should plan the return leg as the one that fills the truck.

Practical guidance

• Below about twenty units, ask about collection or consolidation before accepting an LTL quote.
• Give your supplier date flexibility. It is the input that lets them put you on an existing lane.
• If you buy regularly, ask where the break point is for your postal code and size orders around it.
• Quote delivered rather than ex-works, so you compare one number rather than two.

Working out your own density

The calculation is trivial and worth doing before you accept any quote.

1. 01Measure the shipping unit including the pallet: length, width and height in inches.
2. 02Multiply the three and divide by 1,728 to get cubic feet.
3. 03Divide the total weight in pounds by the cubic feet.
4. 04That number is your density in pounds per cubic foot, and it is what drives the class.

For a 275 gallon IBC: 48 × 40 × 46 = 88,320 cubic inches, divided by 1,728 is 51.1 cubic feet. At 145 pounds that is 2.8 pounds per cubic foot.

Why the return leg is the expensive one

In any returnable programme the two directions are not symmetrical, and designing as though they are is the most common planning error.

Which means the retrieval leg should be planned as an occasional large consolidation rather than as a mirror of the delivery schedule. Programmes that try to return containers on the same rhythm they were delivered spend a great deal on air.

Accessorials, briefly

The charges that surprise people on LTL are not the base rate. They are liftgate, residential delivery, limited access, inside delivery, appointment scheduling and detention.

For containers, liftgate and limited access are the two that bite. A container weighs 145 pounds empty and cannot be hand-unloaded from a trailer without equipment, so if you have no dock and no forklift, that is a liftgate delivery and it should be quoted as one from the start.

The simplest advice

Ask for a delivered price rather than a product price plus freight. It forces the whole cost into one number you can compare, and it puts the burden of load planning on the party who actually knows the lanes.

Questions about shipping

Can containers be shipped stacked on an LTL pallet? Empty, sometimes, if they are banded into a stable unit. Carriers vary in whether they will accept it and it changes the dimensions you declare, so agree it in advance rather than assuming.

Does the class change if the containers are full? Completely. Full containers are dense freight and are classed accordingly. They are also weight-limited on the trailer, which caps a load at around eighteen units rather than fifty.

Is it cheaper to ship containers disassembled? No, and it is not really possible. An IBC is a cage, a bottle and a base, and separating them costs labour at both ends for a modest cube saving.

What about international freight? Containers move internationally routinely. The complications are wood-packaging rules if any part is timber, and the fact that used packaging is restricted into some markets.