CourageToGrow
Well-Known Member
Obviously a lot depends on other factors, strains, nutes, soil, container size, growing technique . . . but under a 400w HPS you could easily fit 4-6 plants. I have 6 plants currently under my 250w HPS with 80w flouros as well. But a good guess is 0.5-1 gram per watt on lights. Also it depends on how long you veg your plants for as well, cause if you got 3 foot plants when you being to flower, you'll get a lot more weed then if you have 1 foot plants, although 3 foot tall plants will take a few months to grow in veg.
Simple answer though, 2 plants under a 400w HPS, 2 months vegging from seed, 2 months flowering, you should get around 6 oz roughly.