What size room? Plus how big do you want the plants to be? You could grow 30 tiny plants or 6 bigger plant to one massive plant. I believe it's recommended 1 plant per 100 watts. The light should cover a 4x4 area. Maybe more or less depending on hood and height it hangs.
well i have an entire room that i can dedicate to growing the room is 11 x 12 ft. I only have 1 600 watt hps light, I want to get maximum yeild but I dont know what set up would be best with just 1 light. many small, a few big, etc. the limit for me where i live is 6 mature plants or 12 imature, me and my wife both have cards so I can do 12 mature, 6 mature and 12 imature, etc. i only wanna use 1 light dont wanna run up the bill too much.
Go with 6 plants. Then you have the option to plant outdoors. Or grow smaller plants and go with 12 but you would be better off with 6. I run 1000w with max of 9 plants. Currently I have 6 under it.