if 1.5 feet tall when you start flowering, you can expect it be at between 3-5 feet tall when harvest time comes. Yield should last you a few weeks, also assuming its a female.
If its only 1.5 feet tall and you stopped its vertical growth for a reason, if you can try to put lights around the sides of it to bush that shit out and increase your yield substantially. If you can tell me what kind of lights your using throughout the veg and bloom/flower cycles, I can give you a pretty good idea of your final dry weight (assuming you don't water cure).