If the math doesn't work out quite so neatly for you, round down to the nearest half-inch. This should put you either right on or very close. If, however, it's still not quite right--if your anchor point is back behind your ear, or you can't comfortably drop your nose down on the string, or your bow arm feels over- or under-extended, or the string is frequently slapping you during the shot--you may need to tweak things a bit. Most bows allow for easy draw-length adjustments in half-inch increments without a bow press. But some don't. Always ask about this before you buy a bow. If the make and model you want doesn't allow for easy draw-length adjustments, then get yourself down to the bow shop and have your pro determine your correct draw length precisely before you plunk down your money.