BMI Calculator
Calculate your Body Mass Index and understand your health status instantly.
Your BMI Score
BMI is a useful starting point for understanding your health, but it doesn't distinguish between muscle and fat. For a more comprehensive view, check out our Muscle Mass Calculator.
Clinical Body Mass Standards & Medical References
WHO Clinical StandardBody Mass Index cutoffs, adult nutritional status classification, and weight risk tiering align with World Health Organization (WHO) clinical guidelines.
Frequently Asked Questions
Explore comprehensive answers, mathematical formulas, and helpful guidance for calculating your results.
How is Body Mass Index (BMI) calculated?
BMI is calculated using the Quetelet equation: weight in kilograms divided by height in meters squared (kg/m²), or in imperial units as 703 × weight (lbs) / height (in)².
What are the standard WHO adult BMI categories?
According to the World Health Organization, a BMI below 18.5 is Underweight, 18.5 to 24.9 is Normal weight, 25.0 to 29.9 is Overweight, and 30.0 or higher is classified as Obesity (Classes I–III).
Why can BMI misclassify muscular athletes?
BMI measures total body mass relative to height without distinguishing between skeletal muscle and adipose tissue. Athletes with high lean muscle mass may have a BMI above 25 despite low body fat percentages.
Do healthy BMI thresholds differ by ethnicity?
Yes. Clinical guidelines for Asian populations often define overweight starting at a BMI of 23.0 and obesity at 25.0 or 27.5 due to higher cardiometabolic risk at lower body mass indices.