How much a gallon of flour weighs is highly dependent on how you put the flour into the gallon container. If it is sifted it will weigh much less than if it is packed down. I would guess that a gallon of flour will probably weigh between 10 and 16 pounds if it is not sifted and not packed very much.
Xarsh has mixed fluid volume units with dry volume units and with weight units. Although they have the same name, ounces that make up a pound (i.e., ounces of weight) are not the same thing as ounces that make up a cup (i.e., ounces of volume). It is simple to illustrate this by noting that a gallon of small lead balls will weigh much more than a gallon of flour even though they both contain 128 volume ounces. On the other hand, 8 pounds of lead balls weighs exactly the same as eight pounds of flour, and they both contain 128 weight ounces.
The use of the same name for these two different types of units is most likely because one fluid ounce of water at room temperature weighs almost exactly one weight ounce.
Actually there are different kinds of pounds. An avoirdupois pound is equal to 16 avoirdupois ounces. A troy pound is equal to 12 troy ounces. Troy weight is used a lot for precious metals and for medicine. The word ounce (1/12 of a troy pound) is derived from the same word as inch (1/12 of a foot). Some interesting relationships can be found throughout our measurement systems.
(accounting for the weight of the jug) the w8 could be calculated lol if you put flour in jug and of course flour can't be described in a gallon of it will have to be w8td in pounds or ounces etc lol lol good question tho!!.