Freight is charged by weight or volume, whichever is greater. To compare them, carriers convert volume (CBM) into an equivalent weight using a ratio that depends on the transport mode. This guide explains CBM to kg conversion for chargeable weight, with our free CBM to KG Calculator.
Conversion ratios
| Mode | 1 CBM equals | Equivalent divisor (cm³/kg) |
|---|---|---|
| Sea freight LCL | 1,000 kg | 1,000 |
| Road freight (common) | 333 kg | 3,000 |
| Express courier | 200 kg | 5,000 |
| Air freight (IATA) | 167 kg | 6,000 |
Ratios can vary by carrier and route; confirm with your forwarder.
Chargeable weight
Chargeable weight = max(actual weight, CBM × ratio)
Examples
Shipment: 1.5 CBM, actual weight 300 kg.
| Mode | Volumetric weight | Chargeable |
|---|---|---|
| Sea LCL | 1,500 kg (1.5 revenue tons) | 1.5 revenue tons |
| Road | 500 kg | 500 kg |
| Courier | 300 kg | 300 kg |
| Air | 250 kg | 300 kg |
Dense vs light cargo
- Dense cargo (metal parts, tiles): actual weight usually decides.
- Light cargo (garments, foam, toys): volume usually decides.
Knowing this helps choose packaging and mode. Read cargo density and weight vs measure.
kg to CBM
Divide weight by the ratio. 500 kg at the air ratio of 167 kg/CBM equals about 3 CBM, meaning a 500 kg air shipment pays by weight unless it exceeds 3 CBM.
For calculating CBM, use the CBM Calculator. For air and courier details, read DIM divisors compared. Estimate total cost with the Freight Cost Calculator.
Why the ratios differ
Each mode has a different balance of space and weight capacity. A ship can carry enormous weight, so sea freight uses a high ratio of 1,000 kg per CBM. Aircraft are limited by both weight and space and are expensive to fly, so the ratio is much lower at 167 kg per CBM. Trucks fall in between. The ratio reflects the typical density at which a vehicle fills up by weight and space at the same time.
Keeping records
Note both actual weight and CBM on your packing list for every shipment. Forwarders need both to quote, and having them ready speeds up bookings and avoids billing disputes later.
Frequently asked questions
How many kg is 1 CBM for sea freight?
1,000 kg for LCL billing (1 CBM = 1 tonne).
How many kg is 1 CBM for air freight?
About 167 kg under the IATA 6,000 divisor.
What is chargeable weight?
The higher of actual weight and volume converted to weight.