BMI Calculator
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kg
Calculate your Body Mass Index instantly | 100% Private
Enter height in cm or ft/in, and weight in kg or lb — instant unit conversion built in.
See exactly where your BMI falls across the WHO adult classification ranges.
Underweight, Normal, Overweight, and Obese thresholds follow WHO adult BMI classification.
All calculations happen in your browser — your health data is never sent anywhere.
Body Mass Index (BMI) is a simple screening measure calculated from a person's height and weight. It's widely used as a quick, low-cost way to categorize weight status at a population level, but it has known limitations for individuals.
BMI = weight (kg) ÷ height (m)². For example, a person who is 170 cm (1.70 m) tall and weighs 65 kg has a BMI of 65 ÷ (1.70 × 1.70) = 65 ÷ 2.89 ≈ 22.5, which falls in the Normal weight category.
Below 18.5 is classified as Underweight, 18.5–24.9 as Normal weight, 25–29.9 as Overweight, and 30 or above as Obese. These ranges are the standard WHO classification for adults and are used by this calculator.
BMI does not distinguish between muscle and fat mass, so athletes and muscular individuals can register a higher BMI without excess body fat. It also does not account for fat distribution, bone density, age, sex, or ethnicity. Use BMI as one general indicator among many, and consult a healthcare professional for a full assessment.
BMI is calculated as weight in kilograms divided by height in meters squared: BMI = weight(kg) / height(m)^2. This calculator handles the conversion automatically if you enter height in feet/inches or weight in pounds.
Using the WHO adult BMI classification: below 18.5 is Underweight, 18.5 to 24.9 is Normal weight, 25 to 29.9 is Overweight, and 30 or above is Obese.
BMI is a general screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, body composition, age, or sex, so athletes and very muscular individuals may show a higher BMI without excess body fat. Always consult a healthcare professional for personalized health advice.
No. All calculations happen locally in your browser using JavaScript. Nothing you enter is transmitted, logged, or stored on any server.
Yes. Use the unit toggle to switch height between centimeters and feet/inches, and weight between kilograms and pounds. The calculator converts these to metric internally before computing BMI.