BMI for children and teenagers: why percentiles are used
Understand BMI-for-age percentiles and why adult cutoffs must not be used for children and adolescents.
Children and teenagers are still growing, so their BMI is interpreted relative to age and sex rather than with adult cutoffs. The calculation itself is the same, but the result is plotted as a BMI-for-age percentile.
CDC categories for ages 2–19 are:
| BMI-for-age percentile | Category |
|---|---|
| Below the 5th | Underweight |
| 5th to below 85th | Healthy weight |
| 85th to below 95th | Overweight |
| 95th or above | Obesity |
A percentile compares the child’s result with the growth-chart reference population of the same age and sex. For example, the 85th percentile means the BMI is equal to or higher than that of about 85% of the reference group; it does not mean 85% body fat.
Accurate birth date, sex, height and weight are required. One percentile is not a diagnosis: growth pattern, puberty, family history and health all matter. Review concerns with a pediatric professional rather than placing a child on an unsupervised diet.
The site’s general BMI calculator can calculate the number, but pediatric interpretation should use an appropriate growth chart.