How to Calculate BMI: Formula, Categories & Limitations

Body Mass Index (BMI) is an epidemiological screening tool developed in the 1830s by Belgian statistician Adolphe Quetelet. It measures body weight normalized for height to assess weight-related health risks across broad populations.

**Metric Formula:** $$\text{BMI} = \frac{\text{Weight in kilograms}}{(\text{Height in meters})^2}$$ **Imperial Formula (Pounds and Inches):** $$\text{BMI} = \left(\frac{\text{Weight in pounds}}{(\text{Height in inches})^2}\right) \times 703$$

- **Underweight**: BMI below 18.5 - **Normal Weight**: BMI 18.5 to 24.9 - **Overweight**: BMI 25.0 to 29.9 - **Obesity Class I**: BMI 30.0 to 34.9 - **Obesity Class II**: BMI 35.0 to 39.9 - **Obesity Class III**: BMI 40.0 and above

BMI is a screening calculation, not a clinical diagnostic tool. It cannot distinguish between bone, water, lean muscle tissue, and adipose fat. High-performing athletes and weightlifters with dense muscle mass are often categorized as overweight despite low body fat percentages.