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CDC BMI-for-age percentile and Z-score for children and teens ages 2 through 20. Enter sex, age (decimals for half-years), height, and weight in US or metric units. See BMI, percentile, weight category, and median BMI at the same age—for education, not diagnosis. Under 2? Use weight-for-length charts with your pediatrician, not BMI-for-age.
Last updated: June 4, 2026
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.
Boy, 10 y, 90 lb, 56 in
BMI 20.2
89.5th percentile
Overweight
Girl, 8 y, 48 lb, 50 in
BMI 13.5
4.7th percentile
Underweight
Girl, 14 y, 145 lb, 64 in
BMI 24.9
90.6th percentile
Overweight
Boy, 16 y, 210 lb, 70 in
BMI 30.1
97.6th percentile
Obesity
| Percentile | Category | Clinical teaching note |
|---|---|---|
| < 5th | Underweight | Review growth velocity, feeding, and underlying illness with pediatrician |
| 5th to < 85th | Healthy weight | Typical CDC screening band—still monitor trends over time |
| 85th to < 95th | Overweight | Discuss lifestyle, labs if indicated, and family history with clinician |
| ≥ 95th | Obesity | Often warrants structured follow-up; not a label to use without clinical context |
| Age | Chart type | Note |
|---|---|---|
| Birth – 23 months | Weight-for-length (infants) | BMI-for-age is not valid—do not use this calculator |
| 2 – 20 years | BMI-for-age (CDC) | Percentile compares to same sex and month of age—what this tool uses |
| ≥ 20 years | Adult BMI cutoffs (kg/m²) | Fixed 18.5 / 25 / 30 bands—different from pediatric percentiles |
| Age | Boys (median kg/m²) | Girls (median kg/m²) |
|---|---|---|
| 5 years | 15.42 | 15.15 |
| 10 years | 16.62 | 16.84 |
| 15 years | 19.83 | 19.91 |
| 18 years | 21.87 | 21.26 |
| BMI (kg/m²) | Pediatric context | Adult BMI table |
|---|---|---|
| 21.5 | Female, 14 y — ~73rd percentile, healthy weight for age | Would be “normal weight” on adult BMI table (18.5–24.9) |
| 24.9 | Female, 14 y — ~91st percentile, overweight for age | Still “normal weight” on adult table (<25)—shows why age matters |
| 30.1 | Male, 16 y — ~98th percentile, obesity for age | Adult “obesity” at ≥30—but pediatric category uses percentile first |
BMI = weight (kg) ÷ height (m)²
Z = [(BMI ÷ M)^L − 1] ÷ (L × S) | Percentile = Φ(Z) × 100
L (lambda) corrects skewness of the BMI distribution at each age. M (mu) is the median BMI at that month. S (sigma) is the coefficient of variation. Values come from CDC's bmiagerev LMS file, interpolated between half-month ages.
Demo boy 10 y: BMI 20.2 vs median 16.62 kg/m² → Z 1.25 → 89.5th percentile (Overweight)
Convert: 90 lb ≈ 40.8 kg; 56 in ≈ 1.42 m → BMI = 40.8 ÷ 1.42² ≈ 20.2 kg/m²
At 120 months, CDC median BMI ≈ 16.62 kg/m² for boys
Z-score 1.25 → 89.5th percentile → Overweight
Between the 85th and 95th percentiles. Follow-up with a healthcare provider for context and next steps.
Teaching point: BMI 20.2 would be healthy on an adult table, but vs peers at age 10 this child is in the overweight percentile band—illustrating why BMI-for-age matters.
BMI ≈ 14.9 kg/m² at median 15.42 → 30.8th percentile (Healthy weight)
Young children often have lower absolute BMI than teens; percentiles account for that—never compare a 5-year-old's BMI number to a 15-year-old's.
Education only. Not for diagnosing obesity, eating disorders, or growth failure. Under-2 infants need weight-for-length assessment. Discuss results with your child's pediatrician.
For parents, school nurses, and students learning CDC growth assessment
Suggested hashtags: #Pediatrics #BMI #GrowthChart #CDC #Calculator