Hey Growmie,
no simple answers to this question as each situation depends on a number of variables. If everything goes well and you use the proper techniques, you can expect to see your plants produce about a gram of weed for every watt of light. To put that in perspective, a skilled grower can use 400 watts HPS grow light to produce 400 grams of pot. That works out to about 14 oz.
Hopefully, I answered your question and remember "Happy Growing" and "Free your mind one puff at a time"