About this calculator
This calculator estimates BMI-for-age percentile for children and teens using CDC growth chart LMS data. Unlike adult BMI, pediatric BMI must be interpreted by age and sex because children are still growing.
Use this result as a screening and conversation aid, not as a diagnosis. A clinician should interpret growth trends, pubertal development, medical history, nutrition, activity, family context, and repeat measurements.
Calculates BMI as kg/m², then uses CDC BMI-for-age LMS parameters by sex and age to estimate z-score and percentile. BMI categories follow CDC child and teen thresholds: underweight below the 5th percentile, healthy weight 5th to less than 85th, overweight 85th to less than 95th, obesity at or above 95th, and severe obesity at or above 120% of the 95th percentile or BMI at least 35 kg/m².
Formula active with CDC LMS data
Educational estimate; not a diagnosis or treatment plan.
Formula and method
BMI = weight in kilograms ÷ height in meters². The calculator then interpolates the CDC BMI-for-age LMS parameters for the entered sex and age. Z-score = (((BMI ÷ M)^L) − 1) ÷ (L × S), then percentile = standard normal cumulative probability of the z-score × 100. The result also compares BMI with the CDC 5th, 85th, 95th, and severe-obesity thresholds.
Frequently asked questions
What age range does this child BMI percentile calculator support?+
It supports children and teens ages 2 through 19. People age 20 and older should use an adult BMI calculator rather than BMI-for-age percentiles.
Why is child BMI different from adult BMI?+
Children and teens are still growing, so BMI is interpreted relative to children of the same age and sex. CDC calls these BMI-for-age percentiles.
What do the CDC BMI categories mean?+
CDC categories are underweight below the 5th percentile, healthy weight from the 5th to less than the 85th percentile, overweight from the 85th to less than the 95th percentile, and obesity at or above the 95th percentile. Severe obesity is defined separately by 120% of the 95th percentile or BMI of 35 kg/m² or greater.
Can BMI percentile diagnose a health problem?+
No. BMI percentile is a screening tool and does not diagnose body composition, nutrition status, or disease by itself. Discuss results and growth trends with a pediatric clinician.
Why might this result differ slightly from the CDC calculator?+
CDC notes that age rounding can cause small differences between calculators. This tool uses completed years and months, then interpolates CDC LMS data; exact date-of-birth calculations may vary slightly.