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ok this is a case of the misposting newbie
dilly post you question in your own thread how big is your grow space, that will help tell ya how big your light needs to be
as for the 2 year old original post.. im gonna say 1 pound off a 400watt light in the past ive had diffrnt lights but i dnt remember yeilds i am a stoner and half the time i dnt weigh it i just smoke it