Each means of conveyance, such as container vessel, truck or aircraft, has a limited space.(volume constraint) Additionally there are weight limitations for all types of modes of transport. (weight constraint)
In order to sell their free spaces more efficiently, international logistics sector developed a concept, which is known as chargeable weight.
According to this concept, first of all transport companies are calculating an hypothetical volumetric weight of the cargo to compare it with the actual gross weight of the goods.
Then, they choose the bigger amount, either actual gross weight or hypothetical volumetric weight. Result is known as the chargeable weight.
Only chargeable weight is used by international logistics companies, when calculating their freight offers.