The standard weight for boys can be calculated by using the body mass index. Body mass index, or BMI, is a measure of the body’s fatness and thinness, as well as the degree of health. It is calculated by dividing the weight by the square of the height. Since the BMI has a normal standard range, the weight can be calculated by the BMI under the condition that the height is known. And BMI is usually divided into international and domestic. The international normal range is between 18.5~24.9, greater than or equal to 25 for overweight, greater than or equal to 30 for obese; domestic normal range is between 18.5~23.9, greater than or equal to 24 for overweight, greater than or equal to 28 for obese. In daily life, you can measure the standard weight through the body mass index, maintain a healthy body shape, and avoid excessive thinness or obesity to affect your physical and mental health.