Converting cubic feet into pounds is not a direct calculation because cubic feet is a measure of volume and the pound is a measure of mass. A cubic foot of lead, for example, will weigh a lot more than a cubic foot of feathers. The key to converting volume into mass is to use the density of the object in the equation.or the gold example, use 20 cubic feet. Multiple this number with the density figure to arrive at your answer on how many pounds it would weight. For the gold example, it would be 20 multiplied by 1,204.46 lb. per cubic feet for a result of 24,089.20 lb. of gold in 20 cubic feet.