BMI calculator with WHO classification
Body mass index is body weight in kilograms divided by height in metres squared. The WHO classification applies to adults.
⚠︎ Learning tool for medical education – not for use in patients or for treatment decisions.
Classification (original publication)
| Score | Classification (original publication) |
|---|---|
| < 18.5 | Underweight |
| 18.5–24.9 | Normal range |
| 25.0–29.9 | Overweight (pre-obese) |
| 30.0–34.9 | Obesity class I |
| 35.0–39.9 | Obesity class II |
| ≥ 40 | Obesity class III |
WHO classification
WHO defines overweight in adults as BMI ≥ 25 and obesity as BMI ≥ 30 kg/m². The 2000 WHO report further distinguishes underweight (< 18.5), normal range (18.5–24.9), pre-obese (25.0–29.9) and obesity class I (30.0–34.9), II (35.0–39.9) and III (≥ 40).
Limitations
BMI does not distinguish between fat and muscle mass and says nothing about fat distribution. For children and adolescents, age- and sex-specific percentiles or the WHO BMI-for-age reference apply, not this classification.
FAQ
How is BMI calculated?▾
Weight in kg divided by height in m squared. Example: 70 kg / (1.75 m)² = 22.9 kg/m².
Does the classification apply to children?▾
No. In children and adolescents, BMI is assessed by age and sex (WHO growth reference).
References
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Open in browser Download on the App StoreIntended purpose: learning tool for medical education only. Not intended for use in patients or for diagnostic or treatment decisions; not a medical device. Calculations follow the cited original publications; no guarantee of completeness or correctness. Last updated: 10/2026 · Dr. Pascal Bafteh