Child BMI Calculator
Calculate BMI percentile for children and teens aged 2-20.
Uses CDC growth chart categories based on age and gender.
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Child BMI Percentile
Child BMI is calculated the same way as adult BMI, but interpreted differently using age- and sex-specific percentiles.
Imperial formula: BMI = (Weight (lbs) × 703) / Height (inches)²
Metric formula: BMI = Weight (kg) / Height (m)²
CDC BMI-for-Age Percentile Categories (ages 2–20):
- Below 5th percentile — Underweight
- 5th to 84th percentile — Healthy weight
- 85th to 94th percentile — Overweight
- 95th percentile and above — Obese
Why percentiles matter for children:
- Children’s body fat changes with age
- Boys and girls develop differently
- A BMI of 22 means something very different for a 5-year-old vs a 17-year-old
Note: This calculator provides an approximate percentile. For accurate assessment, consult your child’s pediatrician who can use official CDC growth charts.