Body Mass Index (BMI) is an epidemiological screening metric established to categorize an adult's body weight relative to height. This calculator computes your BMI score instantly using either standard metric (kilograms and centimeters) or imperial (pounds and inches) measurements, cross-referencing your result against World Health Organization (WHO) reference thresholds. Please note that BMI functions strictly as a population-level screening indicator rather than a comprehensive individual medical diagnosis, as it does not directly measure body fat percentage or visceral adiposity.
BMI is calculated by dividing body weight by height squared. In metric units, divide weight in kilograms by height in meters squared (kg/m^2). In imperial units, divide weight in pounds by height in inches squared and multiply the resulting fraction by 703.
The World Health Organization defines adult BMI categories as Underweight (below 18.5), Normal Weight (18.5 to 24.9), Overweight (25.0 to 29.9), Obese Class I (30.0 to 34.9), Obese Class II (35.0 to 39.9), and Obese Class III (40.0 or higher).
Because BMI relies solely on total weight without differentiating between skeletal muscle mass and adipose fat tissue, highly trained athletes with substantial muscle mass frequently register in the overweight or obese BMI ranges despite maintaining very low, healthy body fat percentages.
Adult BMI categories use fixed, static cutoff numbers regardless of age or gender. For children and teens aged 2 to 20, BMI is interpreted using age-and-sex-specific growth percentiles (CDC/WHO growth charts), because body fat levels change dynamically as children grow and mature.
No. BMI does not evaluate body fat distribution, such as visceral fat deposited around abdominal organs, which carries greater cardiovascular risk than subcutaneous fat. An individual can have a normal BMI but still have elevated cholesterol, high blood pressure, or insulin resistance.
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