If you have someone at home to help, draw your bow and arrow, pointing same toward a target or in a safe direction. When at full draw, have the person(standing to the side of bow) mark the arrow at the back of the bow(side away from shooter) with a magic marker. Do this several times because you will have a tendancy to overdraw when being measured. Measure from the string groove in nock to the mark, this will be your draw length. Your draw length may lengthen as you stretch out the shooting muscles over time. It won't hurt to cut arrows long for this reason. I would advise to do this several times on different days to get a more consistent measurement.