There is 16 cups in a gallon so it would be the same in US Customary units . Another contributor cautioned: In the world of cooking, one 'cup' is normally taken to mean 8 fluid ounces. But it can be...
There is no single answer to this. It depends on the strength of coffee, the age, size, weight, etc of the person, the condition of their kidneys, if they are sensitive to caffeine/sugar, etc. or a...