BMI Calculator for Kids
For children aged 2–12, BMI is calculated the same way as adults (weight in kg divided by height in meters squared), but the result is plotted on CDC or WHO growth charts that account for age and sex. Children's body composition changes dramatically as they grow — a number that's healthy at age 6 may not be at age 10. This calculator gives you the raw BMI value; for accurate pediatric interpretation, compare it to the CDC BMI-for-age percentile charts.
BMI Calculator
Enter your height and weight to calculate your Body Mass Index.
BMI Categories
WHO classification of Body Mass Index ranges.
| Category | BMI Range | Status |
|---|---|---|
Underweight | < 18.5 | May indicate nutritional deficiency |
Normal | 18.5 – 24.9 | Lowest health risk |
Overweight | 25 – 29.9 | Moderate increased risk |
Obese I | 30 – 34.9 | High risk |
Obese II | 35 – 39.9 | Very high risk |
Obese III | 40+ | Extremely high risk |
Frequently Asked Questions
- How is BMI different for children?
- Children's BMI is age- and sex-specific. Instead of fixed categories (underweight, normal, overweight), pediatricians use percentiles: healthy weight is the 5th–85th percentile for the child's age and sex. The CDC provides standardized growth charts used by most pediatricians in the US.
- At what age can BMI be calculated for children?
- BMI-for-age charts are available from age 2. For children under 2, weight-for-length charts are used instead. The adult BMI categories (18.5–24.9 = normal) should not be applied to children — always use age-specific percentile charts.
- My child's BMI is above the 95th percentile. What should I do?
- A BMI above the 95th percentile is classified as obese for children. This doesn't necessarily mean a dire health problem — growth spurts, puberty timing, and muscle mass all play roles. Consult your pediatrician, who can assess growth trends over time and recommend appropriate next steps.
Medical disclaimer: BMI is a screening tool, not a medical diagnosis. It does not measure body fat directly and does not account for muscle mass, bone density, age, sex, or ethnicity. Consult a healthcare provider for personalized health advice.
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