BMI Calculator for Kids and Teens (BMI-for-Age Percentile)
Find a child or teen’s BMI-for-age percentile (ages 2–19) from CDC growth chart data, with weight status and the healthy weight range for their height.
For children and teens, BMI has to be compared with other children of the same age and sex, because body fat changes a lot as kids grow. This calculator works out BMI and places it on the CDC BMI-for-age growth charts for ages 2 through 19, giving a percentile, a weight status and the healthy weight range for the child’s current height.
How to use this tool
- Choose boy or girl and enter the age in completed years and months.
- Enter height and weight in US or metric units.
- Read the BMI-for-age percentile and weight status.
- Use the table to see the BMI and weight at each cut-off for this age and height.
Formula
BMI = kg ÷ m²; z = ((BMI ÷ M)^L − 1) ÷ (L × S); percentile = Φ(z) × 100
L, M and S are the CDC 2000 growth chart values for the child’s sex and age in months, and Φ is the standard normal distribution. Weight status: under the 5th percentile underweight, 5th to under the 85th healthy weight, 85th to under the 95th overweight, 95th or above obesity. Severe obesity is a BMI of at least 120% of the 95th percentile, or 35 or more. Completed months select the corresponding half-month CDC row; weights shown at category boundaries are not treatment targets.
Example
The CDC’s own example is a 12-year-old girl who is 5 ft tall and weighs 136 lb. Her BMI is 61.69 kg ÷ 1.524² m² = 26.6. The 95th percentile for girls of that age is a BMI of 25.3, so she is above it and in the obesity range; her BMI is 105% of the 95th percentile, below the 120% line for severe obesity. At 5 ft, the healthy weight range for her age is about 75.9 to 111.3 lb.
Frequently asked questions
Why not use adult BMI categories for children?
A BMI of 20 can be high for a 6-year-old and ordinary for a 17-year-old. Percentiles compare a child with a large reference group of the same age and sex, so the same cut-offs work at every age.
Does a high percentile mean my child is unhealthy?
Not on its own. BMI is a screening measure; a paediatrician looks at the growth curve over time, family history and other checks before drawing conclusions.
Why is the exact percentile not shown above the 95th?
This tool uses the 2000 LMS reference and reports “95th or above” at the top. CDC also publishes 2022 extended charts for more detailed high-BMI percentiles; those extended calculations are not implemented here.
Which age should I enter?
Completed years and months on the day the child was measured, for example 7 years 4 months.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026