Child BMI Calculator — CDC Percentile Chart for Ages 2 to 19
Calculate BMI for children and teens aged 2 to 19 using official CDC BMI-for-age percentiles. Age and sex specific weight status, the way it should be measured for a growing child. Free and private.
Last updated: June 2026
Please enter an age between 2 and 19 years.
Sex
Result
- BMI
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- Percentile
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- Weight status
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BMI is a screening tool only. A healthcare provider should evaluate any child falling outside the healthy range. What counts as healthy changes with age, so a BMI that is healthy at age 8 may be different at age 15.
Medical Disclaimer: This calculator uses CDC reference data for educational purposes only. It is not a medical diagnostic tool. Always consult a paediatrician about your child's growth and health.
About this tool
How child BMI percentiles work
For adults, BMI uses the same cut-offs for everyone. For children and teenagers it cannot, because a growing body has a different healthy amount of fat at every age, and boys and girls differ too. That is why this child BMI calculator compares a child's BMI against the CDC growth charts for their exact age and sex, and reports a percentile instead of a single fixed label.
The calculation works in two steps. First it computes BMI from weight and height in the usual way. Then it uses the CDC's official LMS reference parameters for that age and sex to convert the BMI into a percentile, the same statistical method clinicians use. A result at the 60th percentile means the child's BMI is higher than about 60% of children their age and sex. The CDC weight-status bands are: below the 5th percentile is underweight, 5th to 84th is a healthy weight, 85th to 94th is overweight, and at or above the 95th is obese.
Treat the number as a starting point, not a verdict. A child's growth trend over time matters more than any single reading, and BMI does not measure muscle, build or stage of development. If the result falls outside the healthy band, the right next step is a conversation with a paediatrician who can look at the whole child. Everything here is calculated privately in your browser using CDC reference data, with nothing uploaded.
How it works
Three quick steps — no account, nothing uploaded to a server.
Enter age and sex
Give the child's age in years and months, and sex.
Add weight and height
Enter weight and height in metric or imperial units.
Read the percentile
See the BMI, percentile and CDC weight status.
General health information related to this tool is available from the US CDC BMI and growth chart resources. Last checked July 2026.
FAQ
Frequently asked questions
Why is child BMI different from adult BMI?
Adults use fixed BMI thresholds: under 18.5 is underweight, 25 is overweight and so on. Children are still growing, and a healthy amount of body fat changes a lot with age and differs between boys and girls. So for ages 2 to 19, BMI is compared against CDC growth charts for the child's exact age and sex, and the result is given as a percentile rather than a fixed category.
What is a BMI percentile?
A BMI percentile tells you how a child's BMI compares with other children of the same age and sex. A child at the 60th percentile has a BMI higher than 60% of their peers. The CDC weight-status categories are: below the 5th percentile is underweight, 5th to 84th is a healthy weight, 85th to 94th is overweight, and 95th or above is obese.
How is the percentile calculated?
The calculator uses the CDC's official LMS reference values for BMI-for-age. It computes BMI from weight and height, then uses the L, M and S parameters for the child's age and sex to find a z-score, which is converted to a percentile. This is the same statistical method clinicians use, applied to CDC reference data for ages 2 to 19.
What age range does this cover?
Ages 2 through 19, which is the range the CDC BMI-for-age growth charts cover. For babies and toddlers under 2, weight-for-length charts are used instead, so this tool does not apply. Enter the child's age in years and months for the most accurate percentile.
Should I worry if my child is outside the healthy range?
A single BMI percentile is a screening number, not a diagnosis. Many healthy children sit outside the middle band, and BMI does not measure body composition, growth trends or development. If your child falls in the underweight, overweight or obese range, talk to a paediatrician who can look at the full picture rather than acting on this number alone.
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