Free BMI Calculator – Calculate Your Body Mass Index Online
Body Mass Index (BMI) is a simple, widely-used screening tool that estimates whether a person has a healthy body weight relative to their height. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI remains one of the most common methods used by healthcare professionals for initial weight assessment.
The formula is straightforward: BMI = weight (kg) / height (m)^2. Our calculator does the math for you — just enter your weight in kilograms and height in centimeters, and you instantly see your BMI along with the WHO classification: underweight (below 18.5), normal weight (18.5-24.9), overweight (25-29.9), or obese (30 and above).
While BMI is useful as a quick screening tool, it has important limitations. It does not distinguish between muscle mass and fat mass, so athletes with high muscle density may be classified as overweight despite having low body fat. It also does not account for age, gender, ethnicity, or fat distribution.
For a more complete picture of your health, consider combining BMI with other measurements. Our body fat calculator provides a more detailed assessment of your body composition, while the calorie calculator helps you determine daily calorie needs based on your activity level. You can also check your ideal weight based on height and frame size. BMI is a starting point, not a diagnosis — consult a healthcare professional for personalized advice.