Actually Chris was right. Make sure your broadhead clears your rest (most people prefer around an inch of clearance) and you're good to go. There's too many factors for people to give you an exact number. Remember, alot of people don't take into account the string loop. I have a 28 1/2" draw PLUS a half inch for the string loop.
buy uncut shafts, take them to a shop or have a buddy help you, pull your bow back with finger off your release and have your buddy mark on the shaft where the shaft is on the rest, then depending on your broadhead, add a 1/2 inch to an inch