Airlines have a limited cargo volume as well as a weight limit. To pay for the space cargo occupies, they charge on the greater of actual weight and volumetric weight.
How it is calculated
For air freight the standard divisor is 6,000 cm³ per kg. Multiply length by width by height in centimetres, then divide by 6,000.
A worked example
A carton measuring 60 × 50 × 40 cm weighs 12 kg. Its volume is 120,000 cm³, so its volumetric weight is 20 kg. You are billed for 20 kg, not 12.
Ways to reduce the bill
- Use the smallest carton that protects the goods
- Remove void fill that adds volume but not protection
- Ship flat-packed or nested products where possible
- Consolidate small cartons onto fewer, denser pallets
Why it matters for different goods
Dense goods such as machine parts usually bill on actual weight, because they fill little space. Light and bulky goods such as pillows, plastic items or furniture bill on volumetric weight, so packaging choices change the price more than the product itself.
Check before you ship
- Measure the outside of the packed carton, not the product
- Ask whether the carrier uses 6,000 or 5,000 cm³ per kg as the divisor
- Compare the volumetric result with the actual weight before you book
Road freight uses a similar rule with a 3,000 cm³ per kg divisor, and ocean LCL treats 1,000 kg as one CBM. The estimator shows which weight is being charged.