An item’s density is determined by its Actual Volume and Chargeable Weight
In simple terms, density is the chargeable weight of your item. (Length x Width x Height = Actual Volume / Weight Ratio = Chargeable Weight)
Normally, higher density goods (such as machinery) attract lower per pound/kilo freight charges than low density goods (such as stuffed toys).
Density is one of the most important freight characteristics directly affecting loading efficiency and economy of freight traffic movement.

Low Density Freight

For low density freight the maximum payload is usually controlled by the cubic capacity of the transportation (length x weight x height limits)
Because increases of the transportation size and weight limits increase the payload per trip.
Fewer trips are required to carry the same amount of size.

High Density Freight

High density cargo is cargo whose weight is high compared to its volume.
A vessel tariff in which freight is charged according to weight or volume, whichever yields the highest freight charge, will result in high density freight being charged on a weight basis.