Child BMI Calculator
Calculate BMI for children and teens (ages 2-19) with percentile and weight category.
Supports imperial and metric units.
Child BMI is calculated the same as adult BMI, but interpreted differently using age- and sex-specific percentile charts.
Imperial:
BMI = (Weight in pounds / Height in inches²) × 703
Metric:
BMI = Weight in kg / (Height in meters)²
Unit conversions:
- 1 inch = 2.54 cm
- 1 pound = 0.453592 kg
- 1 foot = 12 inches = 30.48 cm
Weight categories for children (by percentile):
- Underweight: Below 5th percentile
- Healthy weight: 5th to 84th percentile
- Overweight: 85th to 94th percentile
- Obese: 95th percentile or above
Why percentiles matter for children: Unlike adults, children"s body composition changes as they grow. A BMI of 18 is normal for a 10-year-old but could be underweight for a 17-year-old. Percentiles account for age and sex differences.
Important: This calculator provides an estimate. For accurate percentile assessment, consult your pediatrician who uses full CDC or WHO growth charts.