A couple drops. Well how much is a drop? the "metric" drop, 1/20 mL (50 μL ). the medical drop, 1/12 mL (83⅓ μL). the Imperial drop, 1/36 of a fluidram (1/288 of an Imperial fluid ounce , or 1/1440 of a gill ) (approximately 99 μL). an alternate, possibly apocryphal,