BMI for Children and Teens

How is BMI calculated for children and teens?

BMI for children and teens is calculated in the same way for adults, but the interpretation is different. To determine BMI for children or teens, go to the BMI calculator. The interpretation of BMI for children and teens is both age- and sex-specific. See below for interpretation.

Is BMI interpreted the same way for children and teens as it is for adults?

Although the BMI number is calculated the same way for children and adults, the criteria used to interpret the meaning of the BMI number for children and teens are different from those used for adults. For children and teens, BMI age- and sex-specific percentiles are used for two reasons:

• The amount of body fat changes with age.
• The amount of body fat differs between girls and boys.

Because of these factors, the interpretation of BMI is both age- and sex-specific for children and teens. The BMI-for-age growth charts take into account these differences and allow translation of a BMI number into a percentile for a child’s sex and age.

For adults, on the other hand, BMI is interpreted through categories that are not dependent on sex or age.

How is BMI interpreted for children and teens?

After BMI is calculated for children and teens, the BMI number is plotted on the CDC BMI-for-age growth charts (for either girls or boys) to obtain a percentile ranking. Percentiles are the most commonly used indicator to assess the size and growth patterns of individual children in the United States. The percentile indicates the relative position of the child’s BMI number among children of the same sex and age. The growth charts show the weight status categories used with children and teens (underweight, healthy weight, at risk of overweight, and overweight).

BMI-for-age weight status categories and the corresponding percentiles are shown in the following table.

To find results for your child, plot the age and BMI in the following graph and check the corresponding percentlie line:

See the following example of how some sample BMI numbers would be interpreted for a 10-year-old boy.

BMI-for-age percentiles, Girls, 2 to 20 years:

(Click the graph for full view…))

How can I tell if my child is overweight?

CDC and the American Academy of Pediatrics (AAP) recommend the use of Body Mass Index (BMI) to screen for overweight in children and teens aged 2 through 19 years. Although BMI is used to screen for overweight in children and teens, BMI is not a diagnostic tool.

For example, a child who is relatively heavy may have a high BMI for his or her age. To determine whether the child has excess fat, further assessment would be needed. Further assessment might include skinfold thickness measurements. To determine a counseling strategy, assessments of diet, health, and physical activity are needed.