BMI Calculator
Calculate your Body Mass Index (BMI) from weight and height. See your BMI category — underweight, normal, overweight, or obese. Free, 100% in your browser.
Reference
What is Body Mass Index (BMI)?
Body Mass Index (BMI) is a simple numerical value calculated from weight and height using the formula: BMI = weight (kg) / height (m)². Developed by Belgian mathematician Adolphe Quetelet in the 1830s, it was adopted by the World Health Organization (WHO) as a population-level screening tool for weight classification. It is not a diagnostic measure — consult a healthcare professional for personalized medical advice.
WHO BMI categories
Under 18.5: Underweight — may indicate malnutrition, eating disorders, or other health conditions.
18.5 – 24.9: Normal weight — generally associated with the lowest health risk for most populations.
25.0 – 29.9: Overweight — associated with increased risk of cardiovascular disease and type 2 diabetes.
30.0 – 34.9: Obese (Class I). 35.0 – 39.9: Obese (Class II). 40.0+: Obese (Class III / severe obesity).
Important limitations of BMI
BMI is a screening tool, not a diagnostic measure. It does not distinguish between muscle mass and fat mass — a muscular athlete may score as "overweight" while being very healthy. It does not account for age (body composition changes with aging), sex (women naturally carry more fat than men), ethnicity (Asian populations may have higher health risks at lower BMI thresholds), or fat distribution (abdominal fat is riskier than subcutaneous fat). For a more complete picture, healthcare providers use BMI alongside waist circumference, body fat percentage, blood pressure, and blood work.
Privacy
All calculations run 100% in your browser. No weight, height, or health data is sent to any server.