CBM Calculation: Cubic Metres for Cartons, Pallets and Containers

CBM (cubic metres) is the volume of a shipment. To calculate it, convert each dimension to metres and multiply: CBM = length × width × height. A carton of 60 × 40 × 40 cm is 0.6 × 0.4 × 0.4 = 0.096 m³; multiply by the number of cartons for the shipment total. Then compare the total with the usable volume of the container or truck, and check weight separately.

CBM is the language of sea freight and many freight quotes, but on its own it can mislead: cartons never fill 100% of a container, and pallets waste the space above them. Below are the formulas, worked examples and a practical way to choose a container.

How to calculate CBM step by step

1. 1Measure the outside of the package: the longest side as length, then width and height. Include bulges, handles and pallet overhang.
2. 2Convert to metres: centimetres ÷ 100, millimetres ÷ 1,000, inches × 0.0254.
3. 3Multiply length × width × height to get the CBM of one package.
4. 4Multiply by the number of identical packages.
5. 5Repeat for each package type and add the results.

Container and truck volumes

Nominal volumes come from internal dimensions. Usable volume is lower, because cartons rarely divide evenly into the space and pallets leave gaps above and around them. Figures below are typical; exact internal sizes vary by manufacturer.

Check the container's CSC plate or the line's specifications for the exact payload. For details of each type, see shipping container dimensions and semi trailer dimensions.

Worked example: from CBM to container choice

Say an exporter ships 420 cartons of 60 × 40 × 40 cm, 18 kg each.

• Volume: 420 × 0.096 = 40.32 m³.
• Weight: 420 × 18 = 7,560 kg, well under any container payload, so volume decides.
• 20 ft (about 33 m³): too small even on paper.
• 40 ft (about 67 m³): 40.32 ÷ 67 = 60% of nominal volume. It fits on volume, but a CBM total alone does not prove the cartons fit.

Check the pattern. In a 40 ft container (1203 × 235 × 239 cm), turn the cartons with the 60 cm side along the length: 1203 ÷ 60 = 20 rows, 235 ÷ 40 = 5 across, 239 ÷ 40 = 5 high, which is 20 × 5 × 5 = 500 cartons. 420 fit with room for 80 more. In a 20 ft container (589 cm long), the same pattern gives 589 ÷ 60 = 9 rows, so 9 × 5 × 5 = 225 cartons. Turning them 40 cm along the length gives 14 × 5 × 3 = 210, so 225 is the better simple pattern. Two 20 ft containers (450 cartons) would also work; whether that beats one 40 ft is a rate question.

Why you never get 100% of the CBM

• Dimensions do not divide evenly. In the 20 ft example, 9 rows of 60 cm use 540 cm of 589 cm; the last 49 cm is lost unless smaller cartons fill it.
• Pallets waste height. A 1.6 m pallet in a 2.39 m container leaves 0.79 m above it unless something is stacked.
• Non-stackable items block all the space above them.
• Door clearance and securing take a little space at the doors.
• Mixed sizes leave gaps between groups.

That is why forwarders often plan cartons at well under nominal CBM, and why container utilisation is a better measure than raw CBM.

CBM and chargeable weight

Carriers convert volume into a weight to price light, bulky freight. The ratio depends on the mode:

Using the 420-carton shipment: 40.32 m³ would count as 40,320 kg on a sea LCL W/M basis (more than the 7,560 kg actual, so it is charged by volume), or 40.32 × 166.7 ≈ 6,720 kg by air. For air freight, see chargeable weight. For road freight priced by floor space instead of volume, see loading metres.