BMI Calculator
Calculate your Body Mass Index (BMI). Enter your height and weight to learn your health status.
Disclaimer: This tool is for informational purposes only and does not constitute professional accounting, legal or financial advice. Results are estimates; consult a certified advisor for important decisions. Terms of Service.
What Is Body Mass Index (BMI)?
Body Mass Index (BMI) is an internationally recognized screening measure that assesses the ratio of a person's weight to their height. Developed in the 19th century by Belgian statistician Adolphe Quetelet, it is also known as the "Quetelet index." The World Health Organization (WHO) uses it to classify weight status in adults. BMI does not diagnose any disease on its own, but it is a practical starting point for evaluating health risks associated with being underweight, overweight or obese.
How to Calculate BMI: Formula and Example
The BMI formula is simple: divide your weight (in kilograms) by the square of your height (in meters):
BMI = Weight (kg) ÷ Height² (m²)
For example, a person weighing 75 kg and 1.75 m tall has a BMI of: 75 ÷ (1.75 × 1.75) = 75 ÷ 3.0625 = 24.5, near the upper end of the "normal weight" range. If you enter height in centimeters (175 cm), it converts to 1.75 m. The calculator above handles this conversion and the division automatically.
BMI Categories (WHO Classification)
| BMI Range | Category | General Risk |
|---|---|---|
| Below 18.5 | Underweight | Risk of malnutrition |
| 18.5 – 24.9 | Normal | Low risk |
| 25.0 – 29.9 | Overweight | Moderately increased risk |
| 30.0 – 34.9 | Obese (Class 1) | High risk |
| 35.0 – 39.9 | Obese (Class 2) | Very high risk |
| 40.0 and above | Obese (Class 3) | Extremely high risk |
What BMI Does Not Measure: Key Limitations
BMI is a practical screening tool but cannot distinguish body composition. Because it does not separate muscle from fat, it can be misleading in some cases:
- Athletes and muscular individuals: Muscle is denser than fat, so a lean bodybuilder may register as "overweight" or even "obese" despite low body fat.
- Older adults: Muscle mass declines with age, so an elderly person with a normal BMI may still have high body fat.
- Fat distribution: BMI does not show where fat is stored. Abdominal fat (apple shape) carries more cardiovascular risk than hip fat (pear shape).
- Pregnant people and children: Adult BMI ranges do not apply during pregnancy, and children use age- and sex-specific percentile charts.
Measurements That Complement BMI
For a fuller picture, evaluate BMI alongside waist circumference. A waist above 102 cm in men or 88 cm in women signals increased metabolic risk even with a normal BMI. Waist-to-hip ratio and body-fat percentage add further detail.
How to Use This Tool
- Enter your height in centimeters (e.g., 175).
- Enter your weight in kilograms (e.g., 75).
- Your BMI value and category appear instantly.
- Review the result with a professional in the context of your health history.
Maintaining a Healthy BMI Range
Keeping your BMI in a healthy range comes from sustainable habits rather than crash diets: balanced, portion-controlled nutrition, at least 150 minutes of moderate physical activity per week, adequate sleep and stress management. Consult a doctor or dietitian for rapid weight changes.
Disclaimer and Sources
This tool is for informational purposes only and is not a substitute for medical diagnosis. BMI classification is based on World Health Organization (WHO) standards. Base health decisions on professional medical advice.