In metric, one milliliter of water occupies one cubic centimeter, weighs one gram, and requires one calorie of energy to heat up by one degree centigrade--which is 1 percent of the difference between its freezing point and its boiling point. An amount of hydrogen weighing the same amount has exactly one mole of atoms in it. Whereas in the American system, the answer to "How much energy does it take to boil a room-temperature gallon of water" is "Go **** yourself," because you can't directly relate any of those quantities." - Wild Thing by Josh Bazell.
Regardless of the relative merits of metric/imperial units, I did recently learn than there are 231 cubic inches per gallon (or 277.419 for an Imperial gallon).
But what I couldn't find was how many calories of energy it takes to heat up 1 cubic inch of water by 1 degree Fahrenheit. So... how much energy does it take to heat up one cubic inch of water by 1 degree Fahrenheit?