BMI Calculator
Calculate your Body Mass Index (BMI) to understand whether your weight is healthy for your height. Uses World Health Organization (WHO) classification standards.
What is BMI?
Body Mass Index (BMI) is a simple screening measure that uses your height and weight to estimate whether you are in a healthy weight range. It is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). Because it is quick, inexpensive and non-invasive, BMI is one of the most widely used tools in clinical practice and population health worldwide.
How to interpret your BMI
The World Health Organization defines standard BMI categories for adults: a BMI below 18.5 is considered underweight, 18.5 to 24.9 is a healthy weight, 25 to 29.9 is overweight, and 30 or above falls into the obesity range, which is further divided into Class I, II and III. These thresholds help identify potential weight-related health risks, but they are starting points for a conversation with a clinician — not a diagnosis.
The limitations of BMI
BMI does not measure body fat directly and cannot distinguish between muscle and fat. A muscular athlete may register a high BMI despite low body fat, while an older adult who has lost muscle may have a “normal” BMI yet carry excess fat. BMI also does not account for where fat is stored — abdominal (visceral) fat carries greater health risk than fat stored elsewhere. For a fuller picture, clinicians often combine BMI with waist circumference, waist-to-hip ratio and other measures.
BMI across different populations
Research suggests that health risks linked to BMI can vary across ethnic groups. Some studies indicate that people of South Asian descent may face elevated cardiometabolic risk at lower BMI thresholds, which is why some health authorities use adjusted cut-offs for certain populations. If you are unsure how to interpret your result, your doctor can help you understand what your BMI means in the context of your overall health.
Frequently Asked Questions
BMI is a useful screening tool for most adults but has limitations. It does not distinguish between muscle and fat, so it can overestimate body fat in athletes and underestimate it in older adults who have lost muscle mass. It is best used alongside other measures and a conversation with your doctor.
Sources & References
- 1.World Health Organization. Body mass index (BMI) classification and global recommendations.
- 2.National Institutes of Health (NIH). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.
- 3.Centers for Disease Control and Prevention (CDC). About Adult BMI.
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Medical Disclaimer: This tool is for informational and educational purposes only. Results are not a medical diagnosis. Always consult a qualified healthcare professional for medical advice, diagnosis, or treatment. In an emergency, call your local emergency number or visit the nearest hospital immediately.