If you'd like to keep it short and just grow it out to a bob length, that may take as little as six to nine months. Yet to have it grow beyond that to the point where it falls a couple of inches beyond your ears will take at least a year and a half or more. If you want to go shoulder length or longer, that process will take a couple of years.

We are generally assuming that the individual who is looking to approach a pixie cut in stages has hair that is shoulder-length or thereabouts. If your hair is longer than shoulder-length by any significant amount, you probably want to add one or two stages using the same style of cut you have currently, but bringing the length up to the shoulder.