my current grow in a 3x3 had four plants that were flowered b/t 12-14in., i had plenty of room and could have very comforably added another 2-4...indica's grow fatter so i'd roll with 6-7 max...sativas are generally taller and skinnier so i'd go 7-8 max...if u go sea of green u can comfortably fit 20 2-gallon grow bags in my 3x3 room