Q. How many cups does it take to make a gallon?
A gallon has 4 quarts. A quart has 2 pints. A pint has 2 cups. So, multiple 2 cups x 2 pints x 4 quarts and you end up with 16 cups to make up a gallon.
Another way to look at it is that a gallon is 128 ounces while a cup is 8 ounces. If you dive 128 ounces by 8 ounces, you get 16.