12-year-old boy height 158, weight 100 pounds belongs to the normal range. According to the Chinese body mass index measurements 18.5-23.9 is normal, according to the BMI body mass index formula, the boy’s body mass index is 20, within the normal range. According to the BMI formula: BMI is equal to weight (kilograms) divided by height (meters) squared, body mass index (BMI) = weight (50kg)/height (1.58m)^2 = 20. Chinese people’s body mass index is measured as: less than or equal to 18.4 for the body thin, between 18.5-23.9 for normal, between 24-27.9 for overweight, greater than or equal to 28 for obese. Through the above calculations, the boy’s weight in the normal range, 12 years old belongs to the age of the development of secondary sexual characteristics, height and weight growth is also faster, usually pay attention to balanced nutrition, strengthen the movement.