Child BMI Percentile Calculator
Universal BMI tool for children 2-20 years with visual curve comparison. Uses WHO and CDC LMS parameters for precise Z-score calculation.
Analysis
About
Pediatric weight assessment relies on relative position rather than absolute numbers. For children aged 2 to 20, Body Mass Index changes significantly with age and differs between genders. A static BMI number that is "healthy" for a 10-year-old may be "underweight" for a 15-year-old.
This calculator merges World Health Organization (WHO) standards for early childhood with Center for Disease Control (CDC) data for older children. It calculates the exact Z-score—the number of standard deviations a child is from the population mean. The output features a visual bar graph, allowing parents to instantly gauge the gap between their child's metrics and the statistical average (the 50th percentile).
Formulas
We compute the Z-score using the Box-Cox transformation (LMS method):
The resulting Z score represents the distance from the median M in units of standard deviation S.
Reference Data
| Z-Score Range | Percentile Equivalent | Classification |
|---|---|---|
| < -1.64 | < 5th | Underweight |
| -1.64 to 1.04 | 5th to 85th | Healthy Weight |
| 1.04 to 1.64 | 85th to 95th | Overweight |
| > 1.64 | > 95th | Obesity |
| > 3.0 | > 99.9th | Severe Obesity |