I heard a World Class archer give this little test.... Stand next to an open door. Take your bow stance (pretend your drawing a bow) with your hand on the end of the door. Remember to use the same wrist position as your bow. If your bow is a low wrist, place your hand in the low wrist position on the end of the door. Measure (with a tape measure) from the door to the tip of your nose. That's your draw length. I checked this on some very experienced shooters and the biggest error was 1/16" the others were exact. But, they all had longer ata (38" or longer) bows.