The BMI calculator computes Body Mass Index — weight in kilograms divided by height in metres squared — and classifies the result using the WHO international classification. BMI is used in clinical practice as a screening tool for underweight, healthy weight, overweight, and obesity, informing decisions about drug dosing method (actual vs ideal body weight), nutritional supplementation, and referral for weight management. It is not a diagnostic tool and does not account for muscle mass or fat distribution.
| Category | BMI Range |
|---|---|
| Severe underweight | < 16.0 |
| Underweight | 16.0 – 18.4 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese class I | 30.0 – 34.9 |
| Obese class II | 35.0 – 39.9 |
| Obese class III (morbid) | ≥ 40.0 |
According to WHO, a healthy BMI for adults is 18.5–24.9 kg/m². Below 18.5 is underweight. 25.0–29.9 is overweight. 30.0 and above is obese (Class I: 30–34.9, Class II: 35–39.9, Class III ≥40).
BMI is a population-level screening tool and has limitations for individual assessment. It overestimates adiposity in muscular individuals (athletes, bodybuilders) and may underestimate it in elderly patients who have lost muscle mass. Always interpret BMI alongside clinical assessment.