When I was younger my girlfriends and I used to color our hair just for fun. I needed to use 2 boxes each time and my hair was only half way down my back. I'd say pick up three boxes so that you have them if needed. Last year I started coloring my hair to hide the gray. So far each time I have had multiple colors in my hair but I think that may be something that varies from person to person? I do know my natural blond highlights, the few that I actually had, are gone ever since I started coloring my hair.