Cocktails are typically prepared one or perhaps two drinks at a time. Bar measurements mostly equate to small increments and don't include our usual cooking measurements like teaspoons, tablespoons and cups. Our chart of bar drink measurements displays (drops, jiggers, teaspoons, pints, fifths, quarts) and their equivalents in ounces.
Many drink recipes refer to quantities in "parts". This simply means to use equal measures (parts) of each ingredient.