There is no way to predict a child's adult height with certainty, but there are methods to estimate it via X-rays and mathematical equations. These methods provide parents and doctors with an idea of how tall a child may grow to be.
The most accurate way to predict a child's adult height is to determine the child's "bone age" via an X-ray of the hand. Less accurate, but also less intrusive, ways to guess future height include the "two years times two" and "mid-parental" methods.
To determine adult height using the two years times two method, double a boy's height at the age of two or a girl's height at 18 months old. Utilizing the mid-parental method requires adding the height in inches of the child's mother and father together and then dividing by two. To estimate the adult height of a boy, add 2 1/2 inches to the sum. Subtract 2 1/2 inches from the sum to determine the potential height of a girl. The margin of error for this method is approximately four inches plus or minus.
Children often reach an adult height similar to that of their parents. Besides genetics, a number of other factors play a part in determining height. These include nutrition, hormones, medications, medical conditions and genetic conditions.