BMI & Weight
BMI in Children and Teenagers: A Different Scale
Learn how BMI is calculated differently for children and teens using age- and sex-specific percentiles, and what parents need to know.
BMI works differently for children and teenagers than it does for adults. Using adult BMI thresholds on a growing child would be misleading — and potentially harmful. Here's what parents and caregivers need to know.
Why Children Need Different BMI Standards
Children's body composition changes dramatically during growth. A 5-year-old naturally has a different ratio of fat to muscle than a 15-year-old. Boys and girls also develop at different rates. Because of this, childhood BMI is interpreted using age- and sex-specific growth charts, not fixed cutoffs.
Percentiles, Not Categories
Instead of 'underweight' or 'obese' thresholds, pediatric BMI is expressed as a percentile compared to children of the same age and sex. The CDC growth charts are the standard reference in the United States.
- Below 5th percentile: Underweight
- 5th to 84th percentile: Healthy weight
- 85th to 94th percentile: Overweight
- 95th percentile or above: Obese
What to Do If You're Concerned
If your child's BMI percentile falls outside the healthy range, the first step is talking to their pediatrician. Weight concerns in childhood require careful handling — focus on healthy habits, not weight loss. Encouraging active play, family meals, and nutritious food is almost always the right approach.
Never put a child on a diet without medical supervision. The goal is healthy development, not weight reduction.