Freight · 7 min read · reviewed 2026-10-01
Container specs quote internal volume: 76.4 cbm for a 40ft high cube. That number is the product of three internal dimensions and assumes the cargo is a liquid. Cartons are not a liquid. They come in one size, they cannot be cut, and every axis rounds down independently.
On this carton the same 40ft HQ holds 900 cartons — 68.4 cbm of cargo in a 76.4 cbm box. That is 90% of nominal volume, and the rest is air that cannot be filled because no carton fits in the leftover strip. A costing sheet built on nominal cbm overstates capacity by 8.0 cbm, which is roughly a fifth of the container.
The practical consequence is that freight per unit is not a freight question. It is a packing question with a freight answer.
Two constraints, and the smaller one wins.
Geometry. Try all six orientations of the carton against the container floor and height. Take the best, then check whether the leftover strip along the length is wide enough for a second block — on a 40ft box that strip is often 40–80 cm, and on this carton it is worth a column. This is why the calculated count can be higher than a naive one-axis division suggests, and lower than the nominal volume implies.
Payload. The container has a maximum gross weight, and the tare takes a fixed share of it. This shipment weighs 12.6 tonnes against a 26.6 tonne payload — 47% of the limit — so geometry binds and the box is volume-limited. If the product were dense — liquids, ceramics, tile — the weight ceiling would bind instead, and no amount of clever packing would add a single carton.
Knowing which constraint binds tells you what to change. Volume-limited cargo rewards a smaller or denser carton. Weight-limited cargo rewards a lighter product or a lighter pack, and nothing else.
Freight is charged per box, so the box choice is a pricing decision:
| Container | Cartons | Cargo cbm | Volume used | Gross weight | Limited by |
|---|---|---|---|---|---|
| 20ft Standard | 336 | 25.5 | 77% | 4.7 t | volume |
| 40ft Standard | 720 | 54.7 | 81% | 10.1 t | volume |
| 40ft High Cube | 900 | 68.4 | 90% | 12.6 t | volume |
| 45ft High Cube | 990 | 75.2 | 87% | 13.9 t | volume |
The 20ft GP takes 336 cartons, the 40ft GP 720, the 45ft HQ 990. Per unit the ranking depends entirely on the freight differential between them, which is not proportional to the capacity differential — a 40ft container does not cost twice a 20ft, and a 45ft costs substantially more than a 40ft for 12% more space.
The rule that survives across cargo types: divide the freight quote by the calculated carton count, not by the nominal cbm. The box that looks cheapest per container is frequently not the cheapest per unit, and the difference on dense cargo is large enough to reverse the decision.
Palletising is a handling decision that costs volume. A standard Euro pallet is 1.2 × 0.8 m and 144 mm high; an industrial pallet is 1.2 × 1.0 m. Both waste floor area when the carton footprint does not divide into the pallet footprint, and both waste height because the pallet itself is not cargo.
On a 40ft HQ, floor-loading this carton gives 900 cartons. Palletising the same carton typically loses 15–25% before you have accounted for the pallet height, and the loss is worst when the carton footprint is close to but not exactly a divisor of the pallet. That is a freight cost, not a warehouse cost, and it should be compared against what the pallet actually saves you in labour at destination.
Two cases where pallets win even so: when the destination charges hourly for unloading, and when the cartons would crush under stacking. Both are real constraints, and neither appears in a cbm calculation.
It assumes uniform, rigid, stackable cartons and orthogonal packing. It does not model mixed SKUs in one container, cartons that crush, overhang, or dunnage. It ignores the door constraint except as a physical block — a carton that passes the door but cannot be turned inside the container is a real failure mode the model will not catch.
It also does not know your forwarder. Line weights, Verified Gross Mass declarations and terminal cut-offs are outside the arithmetic. Treat the count as the engineering answer, then confirm the loading plan with the people who will actually load it.
Each one runs the arithmetic above on your own numbers. The guide explains why the figure is what it is; the tool produces it.
Container Loading Calculator — the same engine that produced every figure on this page, with your carton, your route and your duty rate.
Divide 12,032 × 2,352 × 2,698 mm by your carton dimensions, rounding down on each axis, then check the payload. Nominal volume is 76.4 cbm, but real carton counts typically use 55–70 cbm of it.
About 33.2 cbm nominal and roughly 25–28 cbm of real cartons, depending on how well the carton footprint divides into the floor. The 20ft GP also carries a higher payload than a 40ft, which matters for dense cargo.
Because the leftover space is in a strip too narrow for another carton, or because the container hit its weight limit. Both are normal; the calculator reports which one applies.
Yes, typically 15–25% for a standard pallet, more when the carton footprint does not divide cleanly into the pallet footprint. It is a real freight cost that should be weighed against handling savings.
The guides that answer the question this one usually leads to.
The volumetric weight formula, which divisor applies to air, express and LCL, and how carton density tells you whether you pay for space or weight.
Read next → CostingThe five-line landed cost method, one 40HQ to the US worked line by line, and the four charges most costing sheets leave out.
Read next → PricingWhy the deeper tier is not always cheaper per unit once setup costs, freight and carrying cost are counted, and how to find the true break-even quantity.
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