How CBM and chargeable weight are calculated
CBM (cubic metres) is the space your cargo takes up. Carriers compare the real weight with a volumetric weight derived from that space and charge whichever is higher:
CBM = L · W · H · n ÷ 1,000,000
Volumetric weight (kg) = L · W · H · n ÷ divisor
Chargeable weight = max(gross weight, volumetric weight)
Dimensions are in centimetres. The divisor depends on the transport mode. Sea freight uses a fixed ratio of 1 m³ to 1,000 kg instead.
Worked example
Two pallets of 120 × 80 × 100 cm weigh 150 kg each. The total volume is 1.92 m³ and the gross weight 300 kg. By air (1:6000) the volumetric weight is 320 kg, so the airline charges 320 kg. By sea the shipment counts as 1.92 revenue tons, because 1.92 m³ beats 0.3 t.
Divisors by transport mode
| Mode | Divisor | kg per m³ |
|---|---|---|
| Air freight (IATA) | 6,000 | 167 |
| Courier and express | 5,000 | 200 |
| Road freight (common in Europe) | 3,000 | 333 |
| Sea freight LCL | – | 1,000 |
Carriers set their own factors. Road freight in particular varies by country and forwarder, and some charge per loading metre instead.
How much fits in a container?
| Container | Inside volume | Usable in practice | Euro pallets (single layer) |
|---|---|---|---|
| 20 ft standard | 33.2 m³ | about 26 – 28 m³ | 11 |
| 40 ft standard | 67.7 m³ | about 56 – 58 m³ | 23 – 24 |
| 40 ft high cube | 76.4 m³ | about 66 – 68 m³ | 23 – 24 |
Packing never fills a container completely. Above about 15 m³ of LCL cargo, a full 20 ft container is often cheaper.
Tips to lower freight cost
- Measure the outer dimensions of the packed cargo, including the pallet and any overhang. Carriers round up.
- Remove empty space from boxes. For air freight every extra 6,000 cm³ costs as much as an extra kilogram.
- For light, bulky goods compare air, road and sea on chargeable weight, not on gross weight.