Child BMI Calculator
A child’s BMI is calculated the same way as an adult’s, but read differently: it is compared to other children of the same age and sex using percentile charts. Enter height, weight, age and sex for the BMI value and how to interpret it.
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Result
For children and teens, BMI is interpreted by age-and-sex percentile using growth charts (CDC or WHO), not by the adult categories. Use this number with those charts or a pediatrician.
| Percentile | Category |
|---|---|
| Below 5th | Underweight |
| 5th to 84th | Healthy weight |
| 85th to 94th | Overweight |
| 95th and above | Obesity |
Why children use percentiles
Body fat changes a lot with age and differs between boys and girls as they grow, so a fixed BMI cutoff does not work. Instead, a child’s BMI is plotted on a BMI-for-age percentile chart (CDC in the US, or WHO). The percentile — not the raw number — tells you whether the weight is healthy for that age and sex.
Reading the percentile
Roughly: below the 5th percentile is underweight, 5th-84th is a healthy weight, 85th-94th is overweight, and 95th and above is obesity. Because growth is uneven, one reading matters less than the trend over time. Always confirm with a pediatrician before acting.
Informational and educational result. Not a substitute for professional advice.
Frequently asked questions
Sources
- CDC / WHO — BMI-for-age growth charts (ages 2-19)
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