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Adult BMI categories do not work for children, because body fat changes as they grow and differs between boys and girls. Instead a child's BMI is compared with children of the same age and sex — the BMI-for-age percentile.
On CDC charts (used in the US): below the 5th percentile is underweight, 5th to under 85th healthy weight, 85th to under 95th overweight and 95th or above obesity. WHO uses z-scores: above +1 SD overweight and above +2 SD obesity for ages 5–19.
| Sex | Boy |
| Date of Birth | 15 Jan 2016 |
| Date Measured | 15 Jan 2026 |
| Weight | 32 |
| Weight Unit | kg |
| Height | 138 |
| Length Unit | cm |
| Growth chart / country | CDC — United States |
| BMI | 16.8 kg/m² |
| BMI percentile | 53rd percentile |
| Weight category for age and sex | Healthy weight (5th to under 85th percentile) |
| What it means | Out of 100 boys of the same age, about 53 have a lower BMI and 47 a higher one. |
| Z-score (SD score) | 0.09 |
| Median (50th percentile) for this age | 16.63 kg/m² |
| Normal range (3rd–97th percentile) | 13.96 – 23.68 kg/m² |
| Age used | 10 years 0 months |
| Growth chart | CDC (United States) |
| Healthy weight range at this height | 27.1 – 36.9 kg |
BMI 16.8 kg/m²; 53rd percentile; Healthy weight (5th to under 85th percentile).
Try this example →| Sex | Girl |
| Date of Birth | 15 Jan 2012 |
| Date Measured | 15 Jan 2026 |
| Weight | 55 |
| Weight Unit | kg |
| Height | 158 |
| Length Unit | cm |
| Growth chart / country | WHO — India, UK, Australia & most countries |
| BMI | 22 kg/m² |
| BMI percentile | 79th percentile |
| Weight category for age and sex | Normal weight |
| What it means | Out of 100 girls of the same age, about 79 have a lower BMI and 21 a higher one. |
| Z-score (SD score) | 0.81 |
| Median (50th percentile) for this age | 19.57 kg/m² |
| Normal range (3rd–97th percentile) | 15.64 – 26.67 kg/m² |
| Age used | 14 years 0 months |
| Growth chart | WHO (international — used in India, UK, Australia and most countries) |
| Healthy weight range at this height | 38.6 – 56.7 kg |
BMI 22 kg/m²; Normal weight.
Try this example →It depends on sex and exact age: on CDC charts a healthy range is roughly 14–20 for boys and 14–20.5 for girls at 10 years.
Children naturally get leaner and then fatter as they grow, so the same BMI means different things at different ages.
IAP recommends WHO charts up to 5 years and IAP 2015 BMI charts (with adult-equivalent cut-offs of 23 and 27) from 5 to 18 years. This calculator uses WHO 2007 for that age range, which is close.