HEALTH · PEDIATRIC BMI CALCULATOR (CDC BMI-FOR-AGE PERCENTILE)
Pediatric BMI Calculator (CDC BMI-for-Age Percentile)
Calculate your child's BMI percentile using CDC 2000 Growth Charts for ages 2–19. See the BMI-for-age percentile and weight-status category (Healthy weight, Overweight, Obese, Underweight).
CDC BMI-for-age percentile (2–19 years). This is a screening tool only — not a diagnostic result. A healthcare provider interprets BMI in the context of growth trends, development, and clinical assessment.
About This Calculator
Unlike adult BMI, which uses fixed weight-category thresholds, pediatric BMI is expressed as a percentile compared to other children of the same age and sex using the CDC 2000 Growth Charts. A child at the 60th percentile is at or above 60% of children their age and sex. This calculator uses the CDC Lambda-Mu-Sigma (LMS) method to convert BMI to a percentile, applying linear interpolation between age knots for accurate results across the 2–19 age range.
How It Works
Enter your child's age (2–19 years), biological sex, height (cm), and weight (kg). The calculator computes BMI, looks up the age- and sex-specific LMS parameters from the CDC 2000 Growth Chart tables, and applies the LMS formula to calculate the exact percentile. Weight-status categories follow CDC definitions: Underweight (<5th), Healthy weight (5th–84th), Overweight (85th–94th), Obese (≥95th).
The Formula
z = ((BMI/M)^L − 1) / (L × S)
- L
- Lambda (Box-Cox power transformation parameter)
- M
- Mu (median BMI for age and sex)
- S
- Sigma (coefficient of variation for age and sex)
Frequently Asked Questions
- Why is BMI assessed differently for children than adults?
- Children's bodies change dramatically with age, so a fixed BMI threshold cannot define healthy weight. A BMI of 19 is normal for a 15-year-old but high for a 5-year-old. The CDC BMI-for-age percentile accounts for normal developmental changes by comparing a child to a reference population of the same age and sex.
- What do the weight-status categories mean?
- The CDC defines Underweight as below the 5th percentile, Healthy weight as the 5th through 84th percentile, Overweight as the 85th through 94th percentile, and Obese as at or above the 95th percentile. These categories were established based on population data linking BMI percentile ranges to health outcomes.
- Is this a diagnostic tool?
- No. BMI percentile is a screening measure. A high or low percentile does not diagnose a health condition. Only a pediatric healthcare provider can interpret BMI in the context of growth trends, development history, nutrition, and activity level. A single measurement is less informative than a trend over time.
- What is the CDC LMS method?
- The Lambda-Mu-Sigma (LMS) method describes the distribution of BMI at each age using three parameters — a power transformation (Lambda), a median (Mu), and a measure of spread (Sigma). These parameters allow calculation of any percentile point at any age, not just pre-defined cutpoints.