I have a method of getting the yield down to a few grams of buds dry weight. What you do is take the Wattage of the light, not the ballast but the bulb. Then you add your space in sq. meters(you are going to have to convert it to sq. ft., I just don't know what the conversion is. Then you have to figure out how many plants you are going to have in a sq. meter, and how tall are you going to grow them. At this point I figure that it's going to be a guess, and imposable to tell yield. most people can only tell yield from using there own grows as a reference. As for my method of guessing your yield I will tell you the exact yield in 12 weeks.:thumbsup: