Why is Air Freight Calculation So Complicated?
Because a plane is constrained by both volume and weight – thus air cargo service providers need to charge for their services as a function of both volume and weight or they will quickly go out of business.
The airfreight industry's answer to this challenge is Chargeable Weight. Chargeable Weight is the greater of: the Actual Weight of a shipment, or the shipment's cubic volume converted into Volumetric Weight (based on a predetermined cube-to-weight conversion factor called a DIM factor).
Charging for their services based on Chargeable Weight allows air cargo service providers to express their rates in terms of a single unit of measure such as cost per pound or cost per kilo – which is good because it’s simple. The rub is that it isn’t applied per actual pound or kilo – but by Chargeable pound or kilo. There are several key phases in the process of Calculating Chargeable Weight that impact how and what you are charged for a shipment:
Calculating Volume To determine the Chargeable Weight for a shipment one must first calculate its Volumetric Weight. The first step is to calculate the shipment's cubic volume. Conventional logic would suggest that this is as simple as length x width x height x # of cartons. In this case conventional logic would be wrong.
The air cargo industry has its own prescribed method of calculating a shipment's cubic volume, which includes rounding each dimension of a unit/carton (as described on the shipping documents) to the nearest integer BEFORE calculating the cubic volume of the unit/carton -and then summing the cubic volume for the shipment as a whole. This is neither good nor bad – as long as you understand the rules of the game and how they impact