Depending on how long you keep them in you should gain anywhere from 1-3 inches, or at least that was how much length I gained. I keep my braids in for about 2 months and keep them moisturized. It seems that every time I take my braids down I don't realize how much my hair has grown unless I put heat on my hair. Braids also help my hair grow thicker. As for a relaxer taking to the new growth, it should be no problem. HTH