How to calculate BMI
BMI is calculated with the formula BMI = weight (kg) ÷ height (m)². For US units, first convert pounds to kilograms (× 0.4536) and inches to meters (× 0.0254), then apply the same formula.
BMI categories (WHO standard for adults)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
Limitations of BMI
BMI does not distinguish between muscle and fat, and does not account for body composition, frame size, or differences between ethnic groups. Athletes may show a high BMI despite low body fat. Use it as a general screening tool, not a diagnosis.