Carriers charge for space when the parcel is bigger than it is heavy.
Volumetric weight, also called dimensional weight or DIM weight, converts a parcel's size into a weight. The basic formula is length x width x height, divided by a carrier divisor.
The divisor represents the density a carrier expects. A lower divisor creates a higher volumetric weight, which is why express courier shipments often price higher than standard air freight for the same carton.
