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# About BMI for Children and Teens (page 2)

Centers for Disease Control and Prevention
Updated on Sep 3, 2009

### How is BMI calculated and interpreted for children and teens?

Calculating and interpreting BMI using the BMI Percentile Calculator involves the following steps:

1. Before calculating BMI, obtain accurate height and weight measurements.
2. Calculate the BMI and percentile using the Child and Teen BMI Calculator. The BMI number is calculated using standard formulas.
3. Review the calculated BMI-for-age percentile and results. The BMI-for-age percentile is used to interpret the BMI number because BMI is both age-and sex-specific for children and teens. These criteria are different from those used to interpret BMI for adults — which do not take into account age or sex. Age and sex are considered for children and teens for two reasons:

The amount of body fat changes with age. (BMI for children and teens is often referred to as BMI-for-age.)

The amount of body fat differs between girls and boys.

The CDC BMI-for-age growth charts for girls and boys take into account these differences and allow translation of a BMI number into a percentile for a child's or teen's sex and age.

4. Find the weight status category for the calculated BMI-for-age percentile as shown in the following table. These categories are based on expert committee recommendations.

 Weight Status Category Percentile Range Underweight Less than the 5th percentile Healthy weight 5th percentile to less than the 85th percentile Overweight 85th to less than the 95th percentile Obese Equal to or greater than the 95th percentile

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

The CDC BMI-for-age growth charts are available at: CDC Growth Charts: United States.

### 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.

The CDC 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 do not take into account sex or age.