Why Children's BMI is Different
Adult BMI uses fixed cutoffs (e.g., BMI ≥ 30 = obese). For children, a BMI of 22 might be perfectly healthy for a 15-year-old but overweight for an 8-year-old. The CDC uses percentile rankings compared to same-age, same-sex children — not fixed numbers.
Same formula as adults, but interpreted by percentile
Percentile = how the child ranks vs. 100 peers of same age/sex
CDC BMI Categories for Children
| Category | BMI Percentile |
|---|---|
| Underweight | Below 5th percentile |
| Healthy Weight | 5th to less than 85th percentile |
| Overweight | 85th to less than 95th percentile |
| Obese | 95th percentile or above |
Frequently Asked Questions
Is a high BMI percentile always a problem?
Not necessarily. BMI does not measure body fat directly and doesn't account for muscle mass, bone density, or body composition. A child who is very athletic and muscular may have a high BMI percentile without excess fat. Always consult a pediatrician for proper interpretation — BMI is a screening tool, not a diagnosis.
What should I do if my child is in the overweight or obese category?
Consult your child's pediatrician. They can assess whether the BMI reflects actual excess body fat, check for underlying medical conditions, and provide personalized guidance. For most children, the goal is not weight loss but slowing weight gain while the child grows taller into a healthier weight range.
Can I use the adult BMI calculator for teenagers?
No. Adult BMI cutoffs should not be used for anyone under 20. Children and teenagers are still growing, and a BMI that would be classified as overweight in an adult may be completely normal for a 14-year-old. Always use age- and sex-specific percentile charts for children under 20.