BMI for Children and Teens

ExitCare Image Body Mass Index (BMI) is used differently with children than it is with adults.

In children and teens, BMI is used to check weight in relation to height. This is done by measuring the body weight compared to the child's height. It is calculated by dividing weight in kilograms by height in meters squared, or by dividing weight in pounds by height in inches squared and multiplying by 703. Charts are available to figure this out quickly and easily.

Children's body fat changes as they grow. Also, girls and boys differ in their body fatness as they mature. This is why BMI for children, also referred to as BMI-for-age, is gender and age specific. BMI-for-age is plotted on gender specific growth charts. These charts are used for children and teens 2 - 20 years of age.

Each of the charts contains a series of curved lines. These lines show specific percentiles. Healthcare professionals use the charts to identify underweight and overweight children basesd on the following guidelines.

  • Underweight: BMI-for-age less than 5th percentile.

  • Healthy weight: BMI-for-age between the 5th percentile and the 85th percentile.

  • At risk for overweight: BMI-for-age 85th percentile to less than 95th percentile.

  • Overweight: BMI-for-age greater than 95th percentile.

What does it mean if my child is in the 60th percentile?

The 60th percentile means that compared to children of the same gender and age, 60% have a lower BMI.

EXAMPLE

Let's look at the BMI for a boy as he grows. While his BMI changes, he remains at the 95th percentile BMI-for-age.

  • Age: 2 years, BMI: 19.3, Percentile: 95th

  • Age: 4 years, BMI: 17.8, Percentile: 95th

  • Age: 9 years, BMI: 21, Percentile: 95th

  • Age: 13 years, BMI: 25.1, Percentile: 95th

We see how the boy's BMI declines during his preschool years and increases as he gets older.

BMI decreases during the preschool years, then increases into adulthood. The percentile curves show this pattern of growth.

WHY IS BMI-FOR-AGE A USEFUL TOOL?

BMI-for-age is used for children and teens because of their rate of growth and development. It is a useful tool because:

  • BMI-for-age provides a reference for adolescents that can be used beyond puberty.

  • BMI-for-age in children and adolescents compares well to laboratory measures of body fat.

  • BMI-for-age can be used to track body size throughout life.

This information courtesy of the CDC. Editing and layout by ExitCare, LLC.