A cubic foot of what? A cubic foot of feathers is much less than a cubic foot of lead. A cubic foot of water weighs 62.4 lbs per cubic foot. Portland cement weighs 94 lbs per cubic foot.

There are 12 inches in each foot. A cubic foot contains 12^3 or 1728 cubic inches of any substance. So there are 1728 inches of water in one cubic foot.