The cost of a shipment can be affected by the amount of space that it occupies on an aircraft, rather than the actual weight. This is what we call the volumetric weight (or dimensional weight).
What is Volumetric Weight?
The volumetric weight of a shipment is a calculation that reflects the density of a package. A less dense item generally occupies more volume of space, in comparison to its actual weight. The volumetric or dimensional weight is calculated and compared with the actual weight of the shipment to ascertain which is greater; the higher weight is used to calculate the shipment cost.