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 the volumetric (or dimensional) 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.
For example, when you choosing to use the DHL, then
Volumetric Weight = Length x Width x Height / Volumetric Divisor*
* Standard Volumetric Divisor is 5000 for the weight in KG and dimensions in CM or 139 for weights in lbs and dimensions in inches.
So for a big signage, sometimes the DHL door to door delivery cost even would higher than the production cost.