CBM (cubic meter) is the volume of a shipment. You calculate it by multiplying a carton's length × width × height in metres, then by the number of cartons. A 20' holds ~28 m³ of usable space, a 40' ~58 m³ and a 40' High Cube ~68 m³ — never the raw geometric cube, because of the fill factor. This is the number that decides your freight cost and your choice between LCL and FCL.
What CBM is
CBM (cubic meter) is the unit of volume used in ocean and air freight. Unlike weight, volume is very often what your freight bill is based on — especially for light, bulky goods (furniture, plastics, puffed textiles).
The formula is simple. For a carton with dimensions in metres:
CBM per carton = Length (m) × Width (m) × Height (m)
Total CBM = CBM per carton × number of cartons
If your dimensions are in centimetres, divide by 1,000,000:
CBM = (L cm × W cm × H cm) ÷ 1,000,000 × number of cartons
Example: a 60 × 40 × 40 cm carton is 0.6 × 0.4 × 0.4 = 0.096 m³. For 500 cartons, the shipment is 0.096 × 500 = 48 CBM. The method is laid out on tools like the iContainers CBM calculator or Omni Calculator.
To avoid data-entry mistakes and turn cartons into container occupancy instantly, use our CBM calculator.
How many CBM in a container
A container has two very different capacities: its internal geometric volume (the theoretical cube) and its actual loadable volume. Boxy cartons, dunnage, doors, stacking height — you never fill a container to 100%.
| Container | Internal volume | Realistic usable volume | Max payload |
|---|---|---|---|
| 20' Dry (GP) | ~33 m³ | ~28 m³ | ~28,000 kg (often road-capped near ~21,700 kg) |
| 40' Dry (GP) | ~67 m³ | ~55–58 m³ | ~26,700 kg |
| 40' High Cube (HQ) | ~76 m³ | ~68 m³ | ~28,600 kg |
Sources: CBM Calculator — How many CBM in a container, iContainers — 40ft container. Maximum gross weight (container + cargo) is capped at 30,480 kg by the ISO 668 standard, so payload is that ceiling minus the tare (~2.2 t for a 20', ~3.8 t for a 40').
The 40' HQ is only ~30 cm taller inside than the standard 40' (2.69 m vs 2.39 m), yet that adds ~8–10 m³ of usable space. For bulky, light cargo it is almost always the best volume-per-dollar.
The fill factor
The fill factor (foisonnement) is the gap between the theoretical volume of your cartons and the space they actually take once stacked. Two runs of differently sized cartons leave voids; a 55 cm-tall carton stacked two-high "wastes" the remaining metre under the ceiling.
In practice you aim for 85–90% utilisation to allow loading access, dunnage and irregular shapes; the rule of thumb is that "just over 80%" is the practical full (CBM Calculator). Utilisation is measured as:
Utilisation = (Total cargo CBM ÷ Container CBM) × 100
Bottom line: never plan on a 40's raw 67 m³, but on its ~58 m³ usable. That margin is what most beginners forget — and it's why an order that "fits on paper" spills over at the dock.
Volumetric weight vs gross weight
The carrier bills the greater of actual gross weight and volumetric weight. In ocean LCL, the rule is simple: 1 CBM = 1,000 kg. This is the revenue ton — a shipment is billed on the larger of the two, volume or weight.
| Cargo type | Density | Billed on |
|---|---|---|
| Light and bulky (textile, plastic) | < 1,000 kg/m³ | volume (CBM) |
| Dense (metal, tiles, machinery) | > 1,000 kg/m³ | weight |
Example: 4 CBM weighing 900 kg is billed as 4 revenue tons, not 0.9 — volume wins (iContainers, Portlogics). In FCL (full container), the price is a flat rate per box: volumetric weight does not apply, only the max payload matters.
FCL or LCL: from what volume?
- LCL (Less than Container Load, groupage): you pay per revenue ton without booking a whole box. Best under ~10–13 CBM.
- FCL (Full Container Load): a flat rate per container, whatever the fill.
The tipping point is generally around 13–15 CBM (verify with current quotes, as it depends on lane and season): above it, a 20' FCL is often cheaper than LCL while cutting handling and damage risk. This breakeven is part of your landed cost — the true delivered cost of your product.
Pallets vs floor-loaded
- Floor-loaded: cartons stacked by hand, no pallets. You gain ~10–15% of volume (no wood eating height or footprint), at the cost of slower unloading. It's the norm for factory orders in China.
- Palletised: fast forklift load/unload, better protection, but you lose the pallet height and the voids around them. A 20' fits ~10–11 standard pallets, a 40' ~20–21.
The choice depends on your destination warehouse: with no dock or pallet jack, floor-loaded becomes a nightmare. Negotiate it with the supplier before production, not at booking time.
Full worked example
Order: 500 cartons of 60 × 40 × 40 cm.
Volume per carton = 0.6 × 0.4 × 0.4 = 0.096 m³
Total volume = 0.096 × 500 = 48 CBM
In a 40' HQ (~68 m³ usable), 48 CBM is 48 ÷ 68 = 71% fill — comfortable, with room for dunnage. In a 40' GP (~58 m³) it climbs to 48 ÷ 58 = 83%, close to the practical ceiling. A 20' (~28 m³) is out: you'd need two boxes. Verdict: a single 40' HQ, floor-loaded if the destination warehouse allows it.
FAQ
How do you calculate the CBM of a carton?
Multiply length × width × height in metres. A 50 × 40 × 30 cm carton is 0.5 × 0.4 × 0.3 = 0.06 m³. Then multiply by the number of cartons to get the shipment's total CBM. If your dimensions are in centimetres, divide the product by 1,000,000.
How many CBM in a 40ft container?
A standard 40' offers ~67 m³ of internal volume, but only ~55–58 m³ is actually loadable once the fill factor is accounted for. The 40' High Cube reaches ~76 m³ raw, or ~68 m³ usable thanks to its extra 30 cm of height. Always plan on the usable volume, not the raw cube.
Why is my freight billed above the actual weight?
Because the carrier charges the greater of actual and volumetric weight. In ocean LCL, 1 CBM equals 1,000 kg, so light, bulky cargo is billed on volume. That is the "revenue ton" — the larger of CBM or metric tons, whichever is higher for your shipment.
Is LCL or FCL better?
Under ~10 CBM, LCL (groupage) is almost always cheaper. Above ~13–15 CBM, a full container (20' FCL) is often cheaper while cutting handling. The exact point depends on lane and current quotes: compare total delivered cost, not the unit rate.
How many pallets fit in a container?
Roughly 10–11 standard pallets in a 20', and 20–21 in a 40' or 40' HQ, depending on format (Euro pallet 120 × 80 cm or the 110 × 110 cm pallet common in Asia). Floor-loading without pallets gains 10–15% of volume, at the cost of slower manual unloading.
At a trade fair, the real challenge isn't the formula but the data: carton dimensions, units per carton, MOQ. Fairloop captures them product by product at the booth, then computes CBM and container fill automatically — you know before leaving the hall whether your order fits a 20', a 40' or spills over. See the CBM calculator, the landed-cost calculator and our pricing.