Growth plates close between the ages of 12 and 14 in the average female and between the ages of 14 and 16 in the average male. These ages are not absolute; some individuals stop growing earlier or continue to grow past these ages.
The growth plates close at the end of puberty. Individuals who stop growing at a younger age do so because they have reached physical adulthood at a younger age. Those who continue to grow past the average age do so because they are still going through puberty. An orthopedic surgeon can determine whether or not a patient's growth plates have closed using an X-ray.