BMI Calculator
Calculate your Body Mass Index and understand what it means — including its limitations for athletes and strength trainees.
BMI Calculator
Weight ÷ Height²
BMI is a quick general health screening tool, but it has well-known limitations — it doesn't distinguish muscle from fat. A muscular athlete and an obese sedentary person can share the same BMI. For a more meaningful metric, use FFMI or Body Fat %.
Formula: BMI = weight (kg) / height² (m)
BMI Classification Table
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obese (Class I) |
| 35.0 – 39.9 | Obese (Class II) |
| 40+ | Obese (Class III) |
Why BMI Is Misleading for Athletes
BMI (Body Mass Index) was developed by the Belgian statistician Adolphe Quetelet in the 1830s as a population-level statistical measure — not as an individual health diagnostic. It divides weight in kilograms by height in metres squared (kg/m²), producing a single number that categorises you into underweight, normal, overweight, or obese. The fundamental flaw: BMI cannot distinguish muscle from fat. A 90 kg competitive powerlifter at 8% body fat and a 90 kg sedentary person at 35% body fat have identical BMIs but radically different health profiles. Research published in the International Journal of Obesity found that up to 30% of people with normal BMIs have metabolic risk factors typically associated with obesity, while many classified as overweight are metabolically healthy. For strength athletes, the FFMI calculator (Fat-Free Mass Index) is a far more meaningful measure of body composition. That said, BMI remains a useful first-pass screening tool for the general sedentary population and correlates reasonably well with body fat percentage in non-athletic individuals.