LTL freight business is entirely about density. A 53-foot trailer theoretically holds 3816 cubic feet of air (8’ wide by 9′ high by 53′ long). If we loaded air, 3816 cf would be a full load. But we load a wide variety of shapes and sizes, some square, some rectangular, some round, with many pieces irregular in shape which create air pockets, no matter how well the trailer is loaded. So we accept 64 cu. ft. (8’ x 8′) for each lineal foot of trailer as being the practical maximum loading. Therefore, a load with 3400 cubic feet is about as perfect as anyone can get.
The economics are based on the following expectations:
48 foot trailer: 3000 cu. ft. or 30,000 lbs
53 foot trailer: 3400 cu. ft. or 34,000 lbs.
This explains the “conversion factor” of 10 lbs. per cubic foot. This is called density, and is very important in determining freight rates or charges. Most office furniture moves on cube rates, so the density is not a big issue. However, some products are heavy with little cube, so weight (density) is a factor, and we will charge on weight. We treat each lineal foot of trailer deck (floor) as equivalent to 64 cu. ft. (8′ x 8′ x 1’ = 64 cu. ft.) or 640 lbs. This works out to 3392 cu. ft. for a trailer. Sometimes skids are so irregular and awkward that nothing can be loaded on top, so the tariff has a rule for that. When factories load head-loads, they cannot be touched, so rates are based on lineal feet used, and converted to weight or cube, as noted above.