Child BMI Calculator & Key Facts
Key Facts About Child BMI & Percentiles
What is BMI-for-Age?
It is used for children and teens (ages 2–20). The raw BMI number is plotted against the standard growth charts for children of the same sex and age to determine the percentile, which indicates their weight status.
Percentile Categories (CDC Standard)
- Underweight: Less than the 5th percentile.
- Healthy Weight: 5th percentile to less than the 85th percentile.
- Overweight: 85th percentile to less than the 95th percentile.
- Obese: 95th percentile or greater.
Why BMI is Not Perfect
BMI is a screening tool, not a diagnostic one. Very muscular children may have a high BMI due to increased muscle mass, not excess fat. A health professional will consider other factors like family history, diet, and physical activity.
About This Child BMI Calculator
This tool estimates weight status for kids and teens in United States based on age, sex, height, and weight. It calculates a ratio by dividing weight in kilograms by height in meters squared, then compares results to standardized percentile charts. Percentiles indicate categories such as underweight, healthy weight, overweight, or obese.
For ages 2 through 19, percentile ranges vary between boys and girls due to natural growth differences. A value below 5th percentile usually suggests underweight, 5th to 84th percentile indicates healthy weight, 85th to 94th percentile signals overweight, and 95th percentile or higher shows obesity.
To use, input age in years and months, sex, height in inches or centimeters, and weight in pounds or kilograms. Some tools automatically convert units for accurate comparison with national growth charts. Results appear immediately, showing percentile and corresponding category, making it easy for caregivers or educators to track trends over time.
Regular monitoring is recommended, as ratios can change rapidly during growth spurts. While this measure alone does not provide medical diagnosis, it serves as a guideline for evaluating trends relative to peers. This chart-based method is commonly used in pediatric offices, schools, and community programs across United States.