BMI Calculator

Body Mass Index (BMI) is one of the most widely used measures in public health and clinical medicine. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI provides a simple numerical relationship between a person's weight and height. The World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and national health services worldwide use BMI to screen for weight categories that may lead to health problems. While it is not a diagnostic tool on its own, BMI serves as a useful starting point for identifying potential health risks related to body weight.

The BMI formula divides a person's body mass (in kilograms) by the square of their height (in meters). This produces a single number expressed in units of kg/m².

For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 × 1.75) = 22.9 kg/m², which falls within the normal weight category. In imperial units, the formula is: weight (lbs) × 703 / height (in)².

While BMI is a convenient screening metric, it has well-documented limitations that clinicians and researchers recognize:

• BMI does not distinguish between lean muscle mass, bone density, and body fat. Athletes and muscular individuals may be classified as overweight or obese despite having low body fat percentages.
• BMI does not account for fat distribution. Visceral (abdominal) fat is strongly associated with cardiovascular disease and type 2 diabetes, but BMI cannot measure where fat is stored in the body.
• The standard BMI thresholds were developed primarily from data on European populations. Research suggests that health risks associated with a given BMI may vary across different ethnic groups — for example, some Asian populations experience elevated risk at lower BMI values.
• BMI is designed for adults aged 20 and older. For children and adolescents, BMI is interpreted using age- and sex-specific percentile charts published by the WHO or CDC, as body composition changes significantly during growth and development.