Why is child BMI different from adult BMI?
Children’s body composition changes as they grow. Their BMI is therefore compared with children of the same age and sex rather than fixed adult BMI cutoffs.
Child BMI Calculator
Compare a child or teen’s BMI with CDC age- and sex-specific growth references to see the estimated percentile and weight category.
Enter the child’s details
Age and sex are required because healthy BMI ranges change as children grow.
About this calculator
How to use this tool, plus the formulas and logic behind the results.
Tool description
The Child BMI Calculator estimates BMI-for-age percentile for children and teens using CDC growth-chart methods rather than adult BMI categories.
How to use
- Enter the child’s sex, age, height, and weight.
- Choose metric or US units as needed.
- Select Calculate to view BMI and percentile interpretation.
- Compare the result with pediatric guidance from a clinician when needed.
Formulas & reference
BMI = weight ÷ height² (metric basis)Percentile is determined from age- and sex-specific CDC LMS parametersCategories follow pediatric BMI-for-age guidance
Calculation logic
The calculator computes BMI, then maps it to a percentile using CDC child growth data for the child’s age and sex. Adult BMI category labels are not used.
Child BMI FAQ
Understanding BMI-for-age percentiles for children and teens.
What is a BMI percentile?
A percentile shows how a child’s BMI compares with the CDC reference population of the same age and sex. For example, the 60th percentile means the BMI is higher than about 60% of the reference group.
What is a healthy child BMI percentile?
The CDC defines a healthy weight as the 5th percentile through less than the 85th percentile. Results should be considered together with growth patterns and professional advice.
Is one BMI result enough?
No. A child’s growth trend over time is usually more informative than one measurement. A pediatric healthcare professional can review growth history and other health factors.
Which ages can use this calculator?
This CDC-based calculator is intended for children and teens from age 2 through 19. Different growth standards are used for children younger than 2.