Your always want to leave at least an extra inch so that your stylist has something to work with. If you wear your hair at 3-4 inches then you would order 5" or longer. Up to 6" of hair length comes with a standard order. 6" of hair length is a lot so hair and some people feel like they have a real Beatle mob on their head when they do into to see the stylist. They feel uncomfortable sitting and waiting for the stylist. So keep it close to your normal length while still giving the stylist room to work.