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Assess Your Child's BMI


Updated February 15, 2014


Body Mass Index (BMI) is used to assess whether or not children are considered underweight, overweight, or at risk of becoming overweight. As of 2003, your child's BMI should be recorded at each well doctor's visit. (Physicians have used BMI to assess adults' weight for some time now, as it is considered a more accurate predictor of the risks for health-related weight issues.)

BMI is calculated using a formula that measures weight in kilograms in ratio to height in meters squared. BMI determines whether a weight is appropriate for a given height. The formula for and guidelines on children's BMI are different from the formula and guidelines for adults.

To calculate your child's BMI, begin by weighing your child on an accurate scale and measuring your child's current height. The CDC provides guidelines on how to weigh and measure your child accurately. Next, do the following steps:

  • Convert your child's height to inches.
  • Multiply your child's weight by 703.
  • Divide this number by her height in inches.
  • Divide the resulting number by her height in inches.
  • Use a child's BMI chart to locate the percentile that your child falls into.
You can also use an online children's BMI calculator like the one The guidelines for children's BMI are as follows: Since BMI does not take into account body fat in its calculations, it is possible for some kids to rank in the overweight percentile and not be, such as a very athletic boy with a lot of lean muscle. However, this is not typically the case and most children who fall into the higher percentiles do in fact have excess body fat. If in doubt, talk to your pediatrician.

<a data-cke-saved-href="<a href=" href="<a href=" http:="" pediatrics.about.com="" cs="" usefultools="" l="" bl_bmi_calc.htm"=""> More: About.com Pediatrics BMI Table

BMI charts are gender- and age-specific. Since boys and girls body composition vary between genders and fluctuate with age you will need to use the correct chart for your child to get an accurate result. While BMI decreases during preschool, it is completely normal for it to steadily increase in the following years. It's important for your child's BMI to be assessed at each annual check-up so you and your pediatrician can be aware of any trends that are cause for concern.

More Resources from About.com Pediatrics:


Centers for Disease Control. Overweight and Obesity: Childhood Overweight DNPAO CDC. 7 April 2008.

Centers for Disease Control. BMI - Body Mass Index: BMI for Children and Teens: About DNPAO CDC. 7 April 2008.


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