A shot of liquor or liqueur at any bar that I have been to is 1 oz. There are
34 ounces to a liter, therefore 34 shots. I was told you multiply the total
cost of the drink by 3. So since you serve 1.5 oz per shot, 5 times cost is
good. Other bars may calculate differently.
http://www.webtender.com/handbook/measurements.html