BMI Calculator

Body Mass Index (BMI) is a simple measure that uses your height and weight to estimate whether you are underweight, normal weight, overweight, or obese. It is calculated by dividing weight in kilograms by the square of height in meters: BMI = kg / m².

The World Health Organization defines four categories: Underweight (BMI below 18.5), Normal weight (BMI 18.5 to 24.9), Overweight (BMI 25 to 29.9), and Obese (BMI 30 and above). Obesity is further divided into Class I (30-34.9), Class II (35-39.9), and Class III (40+).

BMI does not distinguish between muscle and fat mass. Athletes and muscular individuals may have a high BMI without excess body fat. BMI also does not account for age, sex, bone density, or fat distribution. It is a screening tool, not a diagnostic measure of health.

BMI is often inaccurate for athletes because muscle weighs more than fat. A bodybuilder with very low body fat may be classified as "overweight" or "obese" by BMI alone. For athletes, body fat percentage, waist-to-hip ratio, or DEXA scans provide more accurate assessments.

BMI is a ratio of weight to height and does not measure body composition. Body fat percentage directly measures the proportion of fat tissue in your body. A healthy body fat percentage is typically 10-20% for men and 18-28% for women, but BMI cannot determine this.