Comments by J. Wilson. Thanks to "Kirbo33" for sending an e-mail saying there was a error.

A structure with 12 inches on a side is 12 x 12 x 12 = 1728 cubic inches.

To convert to feet use the conversion 12 inches = 1 foot

So then a structure with 1 x 1 x 1 = 1 cubic foot.

It looks like about 4-5 gallons make up a cubic foot, but how can we actually find out?

Gallon

2.54 cm = 1 in

12 in = 30.48 cm

1728 cubic inches = 929.0304 cubic cm

(Here is the error. The number of cubic cm in a cubic foot is (30.48)^3 rather than (30.48)^2. So this number should be 28316.85 cubic cm.)

1 cubic foot = 929. 0304 cubic cm (should be 28316.85 cubic cm)

1 cubic cm = 1 mL

29.57353 mL = 1 fl oz.

(I assume this came from a reference. It is correct. Apparently it was used to determine that there are 957 oz in a cubic foot -- divide 28316.85 by 29.57.353.)

20 fl oz = 1.25 pts (Or, simply, 16 oz in a pint)

8 pts = 1 gallon

(So, there are 128 oz. in a gallon.)

There are 4.0745833936 gallons in a cubic foot.

(No. Since there are 128 oz in a gallon and 957 oz in a cubic foot, we can determine the approximate number of gallons in a cubic foot by dividing 957 by 128; that is, 7.48.)

(Thus the answer to the original questions is: There are 7.48 gallons in a cubic foot.)