Tell me about dimensional weight.

Dimensional weight, or volumetric weight, is a measure used to estimate the total weight of an item from its length, width, and height. The global transportation industry adopts this technique to estimate a minimum charge for the cubic space of a package. 

In 2015, UPS and FedEx announced to charge all shipments based on the greater of their actual weight and dimensional weight of a package. 

Click to see how main shippers calculate Dimensional Weight:
DHLUPSFedEx