The most accurate method of height prediction comes from using a child's "bone age," determined by an X-ray of the hand, but there are several methods you can use at home to get an idea of how tall your child will eventually become. The most common way to estimate a child's adult height is to base it on the parents' heights. Height Calculator. This is a children's adult height prediction calculator based on the linear regression analysis method. Beside this calculator, another simply way to predict the adult height for a children is simply double the height achieved by . Please enter the values below and hit the submit button to calculate your adult height.