Child & Teen BMI Calculator

Enter your child’s height, weight, and age to calculate their BMI and percentile. Plus, see their body mass classification, according to the CDC growth percentile charts.

Age:
Gender:
Gender:

Child's Body Mass Index (BMI):

 
 
percentile
Scale showing range of child BMI percentiles and their BMI classifications.
Scale showing the CDC classification for this BMI based on the BMI percentile.[1]
This calculation is based on CDC growth chart percentile data,[2] but it is not a prescription for you or your child's health and nutrition. Consult with your doctor before making a change to you or your child's nutrition or diet


How to calculate BMI for children

BMI, or body mass index, is a helpful tool for determining weight and health status for both adults and children. It is a simple formula that uses height and weight to provide you with an idea of where your child falls within certain weight categories.

To calculate BMI, you only need to know your child’s current height and weight. The formula for BMI is:

BMI = weight [kg]height² [m²]

Imperial Units

BMI = weight [lb]height² [in²] × 703

This formula for BMI is the same for adults and children. However, the value is interpreted differently in children. In kids and teenagers, BMI is age and sex-specific.

This is because body fat and weight standards change with age and sex due to different body structure and hormone fluctuations.

As an example, an 8-year-old girl with a BMI of 22 would fall into the greater than 95th percentile and would be considered obese. However, a 15-year-old girl with a BMI of 22 would fall between the 50th and 75th percentile and would be considered to be a healthy weight.

These BMI charts are available on the CDC website (boys[3] and girls[4]).

Body mass index for-age growth charts from the CDC take into account these differences and show BMI as a percentile ranking rather than falling into underweight, normal weight, or obese categories that are used in adults.

These values were based on data collected from surveys of children from the U.S. population from 1963-65 to 1988-94.[5]

BMI Categories for Children Ages 2-19

Body mass index weight categories for children ages 2-19 defined by the CDC
Weight Category Charting Percentile
Underweight <5th percentile
Healthy Weight 5th to <85th percentile
Overweight 85th to <95th percentile
Obese >95th percentile

Healthy BMI for Children

Unfortunately, childhood obesity has become an epidemic.

A study from JAMA pediatrics found that from 2011 to 2012, 17.3% of children in the United States aged 2 to 19 years were obese. Additionally, 5.9% of children met criteria for class 2 obesity, and 2.1% met criteria for class 3 obesity. In addition, all categories of obesity in children showed an increase over the previous 14 years.[6]

Similar to adults, severe obesity in children is associated with an increased prevalence of heart disease and metabolic risk factors.[7]

In addition, a study from the New England Journal of Medicine also found that children with obesity and its related health issues had higher rates of premature death.[8]

This makes BMI charting in kids an important tool in keeping children within a healthy BMI. Calculating and tracking BMI in children is a useful way to diagnose health issues early on to minimize these risks.

A study from the Journal of Pediatrics found that pediatricians that followed children with BMI charting recognized weight issues at a higher rate compared to only utilizing height and weight charting alone.[9]

The nice thing about the BMI formula is that it is quick and easy to calculate. However, since it only uses these metrics, it also has drawbacks.

For example, it does not take lean body mass, physical activity, or other health conditions into consideration. In older kids and adolescents this may have a bigger influence on weight and body fat and should be taken into account.

By using BMI charts in children and monitoring weight as children age, you can ensure that your children stay at a healthy BMI. This will help avoid chronic health issues associated with obesity.

References

  1. Centers for Disease Control and Prevention, About Child & Teen BMI, https://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/about_childrens_bmi.html
  2. Centers for Disease Control and Prevention, Data Table of BMI-for-age Charts, https://www.cdc.gov/growthcharts/html_charts/bmiagerev.htm
  3. Centers for Disease Control and Prevention, 2 to 20 years: Boys Body mass index-for-age percentiles, https://www.cdc.gov/growthcharts/data/set1clinical/cj41l023.pdf
  4. Centers for Disease Control and Prevention, 2 to 20 years: Girls Body mass index-for-age percentiles, https://www.cdc.gov/growthcharts/data/set1clinical/cj41l024.pdf
  5. Centers for Disease Control and Prevention, About Child and Teen BMI, https://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/about_childrens_bmi.html
  6. Skinner, A. C., & Skelton, J. A., Prevalence and trends in obesity and severe obesity among children in the United States, 1999-2012, JAMA pediatrics, 2014, 168(6), 561-566. https://jamanetwork.com/journals/jamapediatrics/article-abstract/1856480
  7. Skinner, A. C., Perrin, E. M., Moss, L. A., & Skelton, J. A., Cardiometabolic risks and severity of obesity in children and young adults, New England Journal of Medicine, 2015, 373(14), 1307-1317. https://www.nejm.org/doi/full/10.1056/NEJMoa1502821
  8. Franks, P. W., Hanson, R. L., Knowler, W. C., Sievers, M. L., Bennett, P. H., & Looker, H. C., Childhood obesity, other cardiovascular risk factors, and premature death, New England Journal of Medicine, 2010, 362(6), 485-493. https://www.nejm.org/doi/full/10.1056/nejmoa0904130
  9. Perrin, E. M., Flower, K. B., & Ammerman, A. S., Body mass index charts: useful yet underused, The Journal of pediatrics, 2004, 144(4), 455-460. https://www.sciencedirect.com/science/article/abs/pii/S0022347604000927