Bone age is the age of the bones and is determined by examining X-rays of the left wrist and left hand to observe the development of the ossification centers and the closure of the epiphysis. Bone age and age correspond to each other, and generally the difference between the two is about plus or minus one year. In daily life, for the convenience of calculating the relationship between age and height, there is the following formula. 2-12 years old children, age x 5 + 75cm, is the corresponding formula for age and height. Since bone age and age correspond to each other, we can change the age in the formula to bone age, it becomes bone age x 5 + 75cm, which is the correspondence between bone age and height.