Depends on how many you use, I use 4 for each plant, for both veg and flowering, I get about 2-2 and-a-half ounces off each plant. But I'm not a pro by anymeans. Get the book "Buds for less: Grow 8oz of bud for less then $100" by SeeMoreBuds. Its all about using CFL's. It will change your life.