This is the single most common billing dispute in air freight, and in nearly every case nothing has actually gone wrong. The shipment was billed on volumetric weight rather than on what the scale said.
The formula
For air freight, volumetric weight in kilograms is:
length × width × height in centimeters, divided by 6000
You are billed on whichever is greater, that or the actual gross weight. Express couriers use 5000 instead of 6000, which makes the same carton more expensive by air express than by air freight.
A carton 60 × 40 × 40 cm has a volume of 96,000 cm³, so 16 KG volumetric. If it actually weighs 9 KG, you pay for 16. Twenty of those cartons is 320 chargeable kilos against 180 actual, and the invoice is nearly double what the scale suggested.
Why it exists
An aircraft runs out of space long before it runs out of payload. A pallet of cushions and a pallet of ball bearings occupy the same hold; if both were billed by weight the cushions would travel almost free. Volumetric weight prices the space.
What to do about it, in order of effect
Reduce air in the carton. The gap between the product and the box wall is the most expensive air you will ever buy. Trimming 3 cm from each dimension of that 60 × 40 × 40 carton takes it to 57 × 37 × 37, or 13 KG volumetric — an 18% saving for a packaging change.
Ask what divisor is being applied before you book. Air freight uses 6000, express uses 5000, and some consolidators quote 5000 while calling it air freight. On a light shipment that difference is 20%.
Check the density crossover. Roughly 167 kg per cubic meter is the point where actual and volumetric weight are equal for air. Below that density you are paying for volume, and volume is what you should optimize.
Reconsider the mode. Cargo that is very light for its size is the worst possible fit for air. If the deadline allows, ocean bills the same box on a formula that treats volume far more kindly.
Check it against a real tariff
The fixed-weight pages run our live air rates against a known consignment, so you can see the tier effect rather than guess at it: 21 KG from China to the United States, 100 KG on the same lane, 50 KG to Nigeria.
To compare air against the alternatives on your destination, start from the country overview — China to the United States, China to Nigeria, China to Australia — or browse every priced lane on the rate index.
