Stowage factor is the amount of cubic feet it takes to store one long ton of a given cargo. This is used to calculate how much can be carried in a ship, container, or other space. This factor can vary depending on how the material is packed and stowed. Wax has a lower stowage factor in bags (53 cubic feet per ton) then in barrels (73). This means that it takes 20 less cubic feet to store one ton of wax in bags then in barrels. Stowage factor basically tells you how efficently a meterial is packed.
The following formula is used to determine the stowage factor of a given cargo:
f is the stowage factor. 2240 is the amount of pounds in a long ton. v is the volume of one unit of cargo, such as an ingot or bag. w is the weight in pounds of the container.
Here are the stowage factors of some common items:
Tires-100 cubic feet per ton
Coffee-70 in bags
Oranges-88 in cases, 63 in cartons
Source: Marine Cargo Operations by Saurbier and Meurn