BMI-for-Age Calculator for Children & Teens (2–19 Years)

📘 Overview: BMI-for-Age Calculator for Children & Teens

The BMI-for-Age Calculator for Children and Teens estimates a child’s Body Mass Index (BMI) and compares it to standardized percentile curves to determine weight status for ages 2 to 19 years. Unlike adult BMI categories, child and teen BMI assessments account for both age and gender, using LMS (Lambda Mu Sigma) data from the CDC's Extended BMI-for-age Growth Charts.

This calculator helps parents, caregivers, pediatricians, and school health officials track growth trends, identify weight concerns early, and support healthy development.

📐 Formula & Methodology

BMI Formula:

Imperial: BMI = (703 × weight in lbs) / (height in inches)²
Metric:   BMI = weight in kg / (height in meters)²

Z-Score Calculation (LMS Method):

z = [(BMI / M)L – 1] / (L × S)

Where L, M, and S are statistical values derived from CDC reference curves. The z-score is then converted to a percentile to classify the child’s weight status.

📊 Example Calculation

Child: 12 years 6 months old male

Weight: 42 kg
Height: 148 cm

Step 1 – BMI:
BMI = 42 / (1.48²) = 19.17

Step 2 – LMS Values:
L: -2.38585803, M: 18.1387275, S: 0.13299058

Step 3 – Z-score:
z ≈ 0.39 → Percentile ≈ 65.2%

Result: Healthy weight category

📈 CDC BMI-for-Age Growth Curve

This chart shows the median BMI trend for boys and girls from ages 2 to 19 years, based on CDC growth data.

🧠 Use Cases

• 🩺 Pediatric health evaluations
• 🏫 School or sports health screenings
• 👪 Parental monitoring of child growth
• 📈 Tracking childhood obesity trends
• 📚 Educational and research purposes

❓ Frequently Asked Questions