How many gallons of water in one cubic foot of ice?

Slightly more than one cubic foot of ice, because water in its solid phase takes up more space than water in its liquid phase. To have a perfectly correct answer, it would depend on the temperature

• water is the most dense at 4 degrees Celcius. Short version, ice

expands due to the way the molecules of water arrange themselves in a very regular pattern in ice - water molecules can "slop past" each other, and thus can occupy less space.