BMI percentile for children compares a child's BMI to peers of the same age and sex using CDC growth chart data. Unlike adult BMI, children's BMI is interpreted relative to normative data — not fixed cutoff values.
Calculate Child BMI Percentile
How to Use the Pediatric BMI Percentile Calculator
This BMI percentile calculator for children uses CDC growth chart LMS parameters to estimate where a child's BMI falls relative to same-age, same-sex peers.
Step 1: Enter Age Accurately
Enter the child's age in years and optionally months. The calculator covers ages 2–19. BMI percentile norms change significantly month by month, especially in young children, so including months improves accuracy.
Understanding Percentile Categories
A BMI at the 60th percentile means the child has a higher BMI than 60% of same-age peers — this falls within the healthy range. The 5th to 84th percentile is considered healthy. The 85th–94th percentile is overweight; 95th percentile and above is classified as obese per CDC definitions. Below the 5th percentile is underweight.
Frequently Asked Questions
Is this pediatric BMI calculator free?
Yes, completely free with no signup required.
Why is BMI percentile used for children instead of adult BMI categories?
Children's BMI changes with age and differs between boys and girls, so raw BMI values can't be interpreted the same way as adults. CDC growth charts compare a child's BMI to thousands of children of the same age and sex, expressing the result as a percentile rank rather than a fixed category.
What is a healthy BMI percentile for children?
Per CDC definitions: Underweight = below 5th percentile; Healthy weight = 5th to below 85th percentile; Overweight = 85th to below 95th percentile; Obese = 95th percentile or above. Note that BMI is a screening tool, not a diagnostic measure — a healthcare provider should evaluate context.
How accurate is this calculator?
The calculator uses an approximation of CDC LMS parameters and produces results that closely match the CDC's own online tool. For clinical decisions, use the official CDC BMI percentile calculator or consult a pediatrician.
At what age can adult BMI categories be used?
Adult BMI categories (underweight <18.5, normal 18.5-24.9, overweight 25-29.9, obese ≥30) are used for adults aged 20 and older. For ages 2-19, percentile-based interpretation is the clinical standard.