50 cubic feet of space = 374.03 gallons of space (rounded),regardless of what's in the space. Even if it's empty.
Cubic feet means a volume with three dimentions. Feet means a length or distance with only one dimension. One cannot be converted into the other.
1 706 gallons
616 x 7.48 =4607.68
50 cubic feet = 50 * 12 * 12 * 12 cubic inches = 86400 cubic inches