Calculate your Body Mass Index (BMI) and health category to track fitness goals.
The Body Mass Index (BMI) is a mathematical formula developed in the 1830s by a Belgian mathematician and sociologist named Lambert Adolphe Jacques Quetelet. It was originally known as the Quetelet Index.
Quetelet was not a physician; his goal was to define the "average man" using statistics, not to create a diagnostic tool for individual health.
The calculation is surprisingly simple. It does not measure body fat directly. Instead, it measures total mass relative to height:
BMI = Weight (kg) / [Height (m)]²If you use Imperial units (pounds and inches), the formula requires a scaling conversion factor of 703:
BMI = (Weight (lbs) / [Height (inches)]²) × 703Because the formula only looks at total mass, it cannot distinguish between fat mass and muscle mass. A professional athlete or bodybuilder might have a BMI of 32 (technically "Obese") despite having extremely low body fat.
Furthermore, the standard healthy ranges (e.g., Normal = 18.5 to 24.9) were calibrated primarily using data from populations of European descent. Studies indicate that South Asian populations face elevated cardiovascular and metabolic risks at much lower BMI thresholds. The World Health Organization (WHO) has established modified criteria for Asian populations, where a BMI over 23 is considered overweight.
Why might a professional athlete with very low body fat be classified as 'Obese' by the BMI scale?