Pediatric BMI Calculator
Calculate BMI for children aged 2–18 with weight-for-age percentile interpretation.
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How to use this calculator
BMI is calculated the same way for children as adults, but interpretation uses age- and sex-specific percentile charts rather than fixed cutoffs. Percentile estimates here are approximated from CDC reference data.
- 1
Enter the child's weight in kilograms.
- 2
Enter the child's height in centimetres.
- 3
Enter the child's age in years (2–18) and select sex.
- 4
Review the BMI result and the age-adjusted weight category.
Frequently asked questions
Why is pediatric BMI interpreted differently from adult BMI?
Children's body composition changes as they grow, so BMI cutoffs vary by age and sex. A BMI of 18 may be healthy for a 5-year-old but underweight for a 15-year-old. Percentile charts account for these changes.
What does the 85th percentile mean?
A child at the 85th percentile has a BMI higher than 85% of children of the same age and sex. Between the 85th and 95th percentile is considered overweight; at or above the 95th percentile is considered obese.
Is BMI alone enough to assess a child's health?
No. BMI is a screening tool, not a diagnostic one. A paediatrician will also consider growth trends over time, diet, activity level, and family history before drawing any conclusions.
What age range does this calculator cover?
This calculator covers children aged 2 to 18 years. For children under 2, weight-for-length charts are used instead of BMI.
Pediatric BMI Calculator for Children
Why Children Need Age-Specific BMI Interpretation
Unlike adults where fixed BMI cutoffs apply, children's healthy weight ranges shift with every year of age and differ between boys and girls. The CDC and WHO use growth percentile charts derived from large population studies to define healthy, overweight, and obese ranges for each age group. This pediatric BMI calculator applies those age- and sex-adjusted boundaries to give a meaningful result.
Acting on Your Child's BMI Result
If your child falls outside the healthy range, the best first step is to speak with a paediatrician. Small lifestyle adjustments — more physical activity, reduced screen time, and balanced meals — are typically the first-line recommendation. Extreme dieting is never recommended for growing children without medical supervision.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →