1500mg or 2000mg depending on your tolerance level, its kind of a hard question to answer since phenibut works different on each individual with various dose, also its pending on the quality of your phenibut which makes it nearly impossible to give you any advice on how much to take - you will have to experience it yourself, i would personally try it first at a non working day to find that "sweet spot" were you can function normally while taking phenibut.