Child BMI Category Calculator
Compute a child’s BMI and see the CDC weight-status category from the BMI-for-age percentile off their growth chart.
How it works
BMI = 703 × weight(lb) ÷ height(in)² · Category by BMI-for-age percentile: <5th underweight, 5th–<85th healthy, 85th–<95th overweight, ≥95th obese
For children and teens, a raw BMI number means little on its own — a healthy BMI at age 4 is very different from age 14. The CDC classifies children by their BMI-for-age percentile, which compares the child to others of the same age and sex. This tool computes the BMI from height and weight, then applies the four CDC categories to the percentile your pediatrician reads off the growth chart at a check-up.
Worked example
A child weighing 70 lb at 50 in tall has BMI = 703 × 70 ÷ 50² = 19.7. If their growth chart puts that at the 60th percentile for age and sex, they are in the healthy-weight category.
Sources: CDC BMI for Children and Teens
Frequently asked questions
Why do I need the percentile — can’t BMI alone give the category?
Not for children. The same BMI is high for a young child but normal for a teenager, so the category depends on age and sex through the BMI-for-age percentile. That value comes from the CDC growth chart your pediatrician plots.
What percentile counts as overweight for a child?
The CDC calls the 85th to below the 95th percentile “overweight,” and the 95th percentile or above “obese.” Below the 5th percentile is “underweight,” and 5th to below 85th is “healthy weight.”
Is this the same as an adult BMI category?
No. Adults use fixed cutoffs (25 = overweight, 30 = obese). Children use age- and sex-specific percentiles, so never apply adult thresholds to a child.
Related calculators
This is a general educational estimate, not medical advice. Every child grows, feeds and responds to medicine differently — for anything about your child’s health, growth, nutrition or medication, follow the guidance of your pediatrician.