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Free pediatric BMI percentile calculator aligned with CDC growth charts. Enter sex, age, height, and weight to get BMI, Z-score, percentile, and standard weight category bands. Ages 2 through 20 only.
Last updated: April 13, 2026
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Sex (for chart reference)
Use decimals for half-years (10.5 = 10 years 6 months).
Measurements
BMI 20.2 kg/m²
89.5th percentile
Z-score: 1.25
Overweight
Between the 85th and 95th percentiles. Follow-up with a healthcare provider for context and next steps.
CDC median BMI at this age/sex: ~16.62 kg/m²
Clinical note
For children under 2, use weight-for-length, not BMI-for-age. Extended very high BMI percentiles may need specialized CDC files—this tool uses the standard LMS file.
Children’s healthy BMI rises with age; percentiles compare your child to the CDC reference population at the same month of life.
Z-score tells how many standard deviations BMI is from the reference median; percentile is the corresponding centile.
Enter 10.5 for ten and a half years so age in months lines up with the half-month LMS grid.
Labels follow widely taught CDC cut points for underweight, healthy weight, overweight, and obesity.
The interpolated M (median) from the LMS curve helps interpret how far above or below “average” the BMI sits.
BMI-for-age is not designed for infants under 24 months; the tool enforces the CDC chart age window.
Boy, age 10, 90 lb, 56 in tall.
BMI 20.2 kg/m²
~89.5th percentile
Overweight
The Centers for Disease Control and Prevention publishes LMS parameters that describe how BMI is distributed at each month of age for boys and girls. The calculator interpolates between the nearest tabulated half-months, computes your child’s BMI from height and weight, derives a Z-score, and maps that to a percentile—matching the approach used in many clinical growth tools.
The same BMI number can fall in different adult vs pediatric categories because the reference median and spread change with age—always use BMI-for-age for youth, not adult BMI tables alone.
Share with parents and educators learning growth assessment.
Suggested hashtags: #Pediatrics #BMI #GrowthChart #Health #Calculator