Well you can stand beside a wall and stick ur arm out straight and put your fist against the wall, now bend your arm slighty as you would hold your bow, have ur guy measure from the wall to the corner of your mouth. Some pro shops measure with your arm straight and that will be wrong, because your bow arm should be slightly bent and relaxed at full draw. Prolly better ways to do it as well, but this is how i was always measured. But keep in mind thats only a starting point, once you get your bow, stay at the pro shop and shoot it and you may have to go up or down 1/2" or so to get it perfect.Psstt go for the BowtechAllegiance.