BMI Calculator
Calculate your Body Mass Index (BMI) using your weight and height. BMI is a widely used screening tool that categorizes weight status based on the WHO classification system.
How This Calculator Works
Formula: BMI Formula with WHO Classification
BMI is calculated by dividing weight in kilograms by height in meters squared (kg/m²). The result is classified using World Health Organization categories: Underweight (below 18.5), Normal weight (18.5-24.9), Overweight (25.0-29.9), and Obesity (30.0 and above). This calculator supports both metric and imperial inputs with automatic conversion.
Limitations
- BMI does not distinguish between muscle mass and fat mass, so muscular individuals may be classified as overweight.
- BMI does not account for age, sex, ethnicity, or body fat distribution.
- BMI is a screening tool and not a direct measure of body fatness or health.
- BMI thresholds may not apply equally across all populations and ethnic groups.
These calculations are estimates based on established formulas. Individual results vary. Consult a healthcare professional before making significant changes to your diet or exercise routine.
Body Mass Index (BMI) is one of the most commonly used metrics for assessing whether a person's weight falls within a healthy range relative to their height. Developed by Adolphe Quetelet in the 19th century, BMI has become a standard screening tool used by healthcare professionals worldwide.
The calculation is straightforward: divide your weight in kilograms by the square of your height in meters. The resulting number is then compared against the World Health Organization's classification system, which defines ranges for underweight, normal weight, overweight, and obesity.
While BMI is a useful starting point for understanding weight status at a population level, it has important limitations at the individual level. It does not differentiate between lean mass and fat mass. An athlete with significant muscle mass may have a high BMI without excess body fat. Similarly, an older adult may have a normal BMI but carry more body fat than expected.
BMI also does not account for where fat is distributed on the body. Research indicates that abdominal fat carries greater health risks than fat stored in other areas. For a more complete picture of body composition, consider using BMI alongside other measurements such as waist-to-hip ratio, body fat percentage, or waist circumference.
Despite its limitations, BMI remains a valuable first-line tool due to its simplicity and the strong correlation it shows with health outcomes across large populations. If your BMI falls outside the normal range, it may be worth discussing with a healthcare provider who can evaluate additional factors specific to your situation.