Calculate BMI, BMI-for-age percentile, and weight category for children and teens ages 2 through 19. Pediatric BMI must be interpreted by exact age and sex because children are still growing.
BMI-for-age categories
| Category | Percentile range |
|---|---|
| Underweight | Below the 5th percentile |
| Healthy weight | 5th to below the 85th |
| Overweight | 85th to below the 95th |
| Obesity | 95th percentile or above |
Information needed
- Sex used by the CDC growth chart
- Exact age in years and months
- Accurate height
- Accurate weight
People age 20 or older should use an adult BMI calculator.
Why children use BMI percentiles
Adult BMI cutoffs are not appropriate for children and teens. A pediatric BMI is compared with children of the same age and sex in the CDC reference population, producing a BMI-for-age percentile.
Measure height and weight carefully
Measure without shoes and heavy clothing. Use a digital scale on firm flooring, record weight accurately, and measure height while standing straight against a flat wall. Small measurement differences can change a percentile near a category boundary.
What does a percentile mean?
A percentile describes how a child’s BMI compares with the reference population of the same age and sex. It is a screening comparison, not a diagnosis or a school grade.
Does BMI directly measure body fat?
No. BMI uses height and weight. Growth pattern, development, family history, physical examination, and other health information provide important context.
When should a parent speak with a clinician?
Discuss concerns about growth, rapid weight change, eating, development, or a BMI result with a qualified pediatric healthcare professional.