CBM and volumetric weight calculation: formulas and examples

CBM stands for cubic meter: the unit of volume that measures a shipment's actual bulk in international transport. It is calculated by multiplying a parcel's length, width and height, expressed in metres, then adding up the volume of each carton or pallet that makes up the shipment.

The formula is Volume (m³) = Length × Width × Height, dimensions taken in metres. When measurements are in centimetres, the product of the three dimensions is divided by 1,000,000 to get back to cubic metres. Take a carton measuring 60 × 40 × 40 cm: the unit volume is 96,000 cm³, or 0.096 m³. For a shipment of 200 identical cartons, the total CBM reaches 19.2 m³.

A cargo aircraft is limited by volume as much as by weight. To avoid carrying light, bulky goods at a loss, IATA (International Air Transport Association), which sets the pricing rules for air freight worldwide, uses a standard volumetric factor of 6,000 cubic centimetres per kilogram, equivalent to a reference density of 166.67 kg per cubic metre.

The formula is Volumetric weight (kg) = (Length × Width × Height, in cm) ÷ 6,000. Take the same 60 × 40 × 40 cm carton: the volume is 96,000 cm³, divided by 6,000, giving 16 volumetric kg. If that carton actually weighs 9 kg, the airline bills on 16 kg: the higher of the two weights is always used.

Express integrators such as DHL apply a stricter volumetric divisor than standard air freight: 5,000 instead of 6,000, equivalent to a reference density of 200 kg per cubic metre. For the same volume, an express shipment is therefore billed on a heavier weight than consolidated air freight.

Take the same 60 × 40 × 40 cm carton, or 96,000 cm³. Divided by 5,000, the volumetric weight reaches 19.2 kg, against 16 kg with the 6,000 divisor of standard air freight: a 20% gap on this item alone. Express remains justified for small, urgent shipments, but becomes costly as soon as volume grows without the actual weight following.

In FCL (Full Container Load), you book an entire container: the price does not depend on the exact CBM loaded inside, but on the capacity of the container booked. In LCL (Less than Container Load), consolidation charges by CBM or by weight, under the W/M convention (weight or measurement): the carrier applies whichever is higher, on the usual basis of one tonne per cubic metre, meaning 1 CBM equals 1,000 kg. This conversion remains a commercial convention, not a regulatory standard: some contracts and some routes use a different threshold, sometimes lower.

Example: a shipment of 3 m³ weighing an actual 900 kg is billed on the equivalent of 3 tonnes, since the converted volume exceeds the actual weight. The same shipment, if it weighed 3,500 kg, would be billed on its actual weight, this time higher than the converted volume. Before booking a consolidation, calculate both values and use the higher one: it is the one the freight forwarder will bill.

The dimensions of shipping containers are standardised by ISO 668, which guarantees comparable capacity from one carrier to another. According to technical specifications published by carrier Maersk, a standard 20ft container offers an internal length of 5.896 m, a width of 2.350 m and a height of 2.393 m, giving a volume of 33 m³ and a maximum payload of 28,200 kg. A standard 40ft container shares the same width and height, with an internal length of 12.032 m, giving 67 m³ and a maximum payload of 28,800 kg. The 40ft High Cube version adds about 30 cm of internal height, up to 2.697 m, giving a volume of 76 m³ and a maximum payload of 28,620 kg.

Theoretical volume is not loadable volume. Palletisation, handling aisles and bracing leave gaps: an 80 to 90% occupancy rate of the theoretical volume is a reasonable benchmark for palletised goods. For the 0.096 m³ carton, a 20ft container theoretically holds around 343; with an 85% occupancy rate, that figure drops to around 290 cartons.

CBM is not just a figure to calculate, it is a negotiating lever. Packaging sized to the product's dimensions, without excess bracing, reduces the volume billed across all three transport modes. Choosing a carton format compatible with the pallet used, the Euro-pallet measuring 120 × 80 cm, limits gaps and increases the number of cartons per pallet and per container.

For a suitable product, flat-pack or knocked-down packaging sharply reduces volume compared with the assembled product, an effective lever for bulky items such as furniture or sports equipment. Always compare the total cost per CBM or per chargeable kilo, including ancillary fees, rather than the headline rate alone. The tipping point between consolidation and a full container generally sits around half a 20ft container, or 12 to 15 m³: below that, LCL remains competitive; above it, FCL is often cheaper per cubic metre.

Sorva is a brokerage and trading house active between Europe and China, with a Chinese-speaking team based in Guangzhou. Before booking freight, our team checks the actual cubic measurement declared by the factory, carton by carton, and calculates the chargeable weight for the mode chosen, air, express or sea. This check avoids the billing discrepancies that often arise between the initial proforma and the actual packing list at loading.

The Produce and deliver package negotiates freight in the same move as the purchase price, from production follow-up through to delivery at your door, weighing up FCL, LCL, air or express depending on your volume, your schedule and the value of the goods. In most cases you pay no fees on sourcing: you open a file, we negotiate the merchandise on your behalf and we take a commission on its ex-works value.