You can decide the right height of the stool in two ways. One is to check it standing: if the guitar stool's seat falls right in the middle of your knees, then it's right for you. Another way to check the guitar stool's height is by sitting on it. If your lap and feet stay straight to the surface after sitting, then it's right. However, if your feet fall flat at the floor but your knees are pointing upward, it's probably too short for you.