There is no scientific definition of the volume of a faucet drip, but after measuring a number of kitchen and bathroom sink faucets, for our calculations below (numbers are rounded), we are going to use 1/4 milliliter (ml) as the volume of a faucet drip. By these drip estimates:
One gallon = 15,140 drips One liter = 4,000 drips
(One other site lists the volume as 1/3 milliliter.)
Simple calculation with an apparent range of + / - 25%
When I was teaching chemistry, I had my students measure how many drips per 10 ml. They averaged close enough to 200 so that one ml = 20 drips. An Imperial pint contains 569ml, so the number of drips calculates to approximately 11,400 drips, depending on who draws the beer.