BMI Calculator
Calculate your Body Mass Index (BMI) to check if your weight is in a healthy range.
Your Measurements
| Category | BMI Range |
|---|---|
| Underweight | < 18.5 |
| Normal | 18.5 - 24.9 |
| Overweight | 25.0 - 29.9 |
| Obese (Class I) | 30.0 - 34.9 |
| Obese (Class II+) | ≥ 35.0 |
Your Result
About BMI Calculator
Body Mass Index (BMI) is a simple screening measure that uses your height and weight to estimate body fat. Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI has become one of the most widely used health indicators. It is calculated by dividing weight in kilograms by height in meters squared: BMI = weight (kg) / height (m)². For imperial units, the formula is BMI = 703 × weight (lb) / height (in)².
While BMI is a useful initial screening tool, it has limitations. It does not directly measure body fat percentage, and factors like muscle mass, bone density, age, sex, and ethnicity can influence its accuracy. Athletes with high muscle mass, for example, may have a high BMI despite having low body fat. For a comprehensive health assessment, consult with a healthcare professional who can consider additional metrics like waist circumference, body fat percentage, and overall fitness level.
BMI Categories (WHO Classification)
The World Health Organization (WHO) defines the following categories: Underweight (BMI < 18.5), Normal weight (18.5–24.9), Overweight (25.0–29.9), Obese Class I (30.0–34.9), Obese Class II (35.0–39.9), and Obese Class III (≥ 40.0). These thresholds apply to adults aged 20 and older and may vary slightly for different populations.
FAQ
Q: Is BMI accurate for athletes?
A: BMI may overestimate body fat in muscular individuals. Athletes with significant muscle mass may have a high BMI but low body fat. For athletes, body fat percentage or DEXA scans provide more accurate assessments.
Q: What is BMI Prime?
A: BMI Prime is your BMI divided by 25 (the upper limit of normal). A BMI Prime of 1.0 means you are at the upper limit of normal weight. Values below 1.0 indicate normal or underweight, and above 1.0 indicate overweight.
Q: Is BMI different for children?
A: Yes. For children and teens (ages 2-19), BMI is interpreted differently using age- and sex-specific percentiles. This calculator is designed for adults aged 20 and older.
Q: Is my data safe?
A: Yes. All calculations happen locally in your browser. No personal health data is sent to any server.