BMI Calculator

Body Mass Index (BMI) is a screening tool that estimates whether a person's weight is in a healthy range for their height. It was developed by Belgian statistician Adolphe Quetelet in the 1830s and became a standard clinical screening tool in the 1970s after epidemiologist Ancel Keys validated its population-level accuracy.

To calculate your BMI, enter your height and weight in either metric or imperial units. The calculator applies the standard formula and places your result in one of four WHO-defined categories: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), or Obese (30.0 and above).

BMI is useful because it is fast, free, and correlates reasonably well with health risk at the population level. Research consistently shows that BMI outside the healthy range is associated with increased risk of type 2 diabetes, heart disease, certain cancers, hypertension, and metabolic syndrome.

However, BMI has important limitations. It does not distinguish between fat mass and lean mass. Highly muscular individuals (athletes, bodybuilders) often have "overweight" or "obese" BMIs despite very low body fat. Conversely, older adults can have a "normal" BMI while carrying dangerous amounts of visceral fat due to muscle loss (sarcopenia). Asian populations may face health risks at lower BMI thresholds than Western reference ranges suggest.

For a more complete health picture, pair BMI with waist circumference (healthy: under 35 inches for women, under 40 inches for men), waist-to-hip ratio, and body fat percentage. These metrics together provide a much fuller picture of metabolic health than BMI alone.

BMI is a starting point for a health conversation — not a diagnosis. Always discuss your results with a qualified healthcare provider before making significant changes to diet, exercise, or medication.