BMI Calculator
Enter your height and weight to calculate your Body Mass Index (BMI) and see which standard WHO category it falls into.
BMI is a general screening measure and doesn't account for muscle mass, bone density, age, or sex — it's not a diagnosis. For a personal health assessment, talk to a doctor or healthcare provider.
About the BMI Calculator
Body Mass Index was developed in the 1830s by Adolphe Quetelet, a Belgian mathematician, as a population-level statistical measure — not as an individual health diagnostic, which is part of why it has real, well-documented limitations when applied to any one person.
The formula and categories
BMI = weight in kilograms ÷ (height in metres)². The World Health Organization's standard adult categories are: under 18.5 underweight, 18.5–24.9 normal weight, 25–29.9 overweight, 30 and above obese.
What BMI doesn't account for
BMI can't distinguish muscle mass from fat mass, which is why very muscular individuals (athletes, bodybuilders) often show as "overweight" or "obese" despite low body fat. It also doesn't account for age, sex-based differences in typical body composition, or where fat is distributed on the body — two people with identical BMI can have very different actual health profiles. It's not designed for use with children, or validated the same way for pregnant women. For these reasons, BMI is best treated as a quick population-level screening number, not a personal diagnosis — a doctor or healthcare provider can give you an assessment that actually accounts for your individual situation.
Frequently Asked Questions
How is BMI calculated?
BMI = weight in kilograms ÷ (height in meters)² — the standard formula used by the World Health Organization.
What are the BMI categories?
Under 18.5 is underweight, 18.5–24.9 is normal weight, 25–29.9 is overweight, and 30 or above is obese, per WHO's standard adult classification.
Is BMI accurate for everyone?
No — it doesn't distinguish muscle from fat, and isn't designed for children, pregnant women, or very muscular individuals. It's a general population screening tool, not an individual diagnosis.