Air carriers charge on whichever is higher, the actual gross weight on the scale or the volumetric weight implied by the cargo's dimensions, so light bulky freight bills on the space it fills rather than on its mass. IATA's general rule fixes the volumetric figure by dividing the shipment's volume in cubic centimetres by 6000, the divisor that turns occupied space into a billable weight for general air cargo. That 6000 divisor is the IATA standard, not a universal constant: express and courier networks set their own, and DHL Express divides by 5000, which yields a higher volumetric weight for the same box. For the booking desk the term decides which figure lands on the invoice, so the cargo's dimensions are checked against the carrier's measured weight before the charge is accepted.
Glossary
Chargeable Weight
The weight an air cargo shipment is billed on: whichever is greater, the cargo's actual gross weight or its volumetric weight, the weight calculated from the space the cargo occupies.