BMI Calculator
Calculate your Body Mass Index and find out what it means for your health.
About the BMI Calculator
BMI (Body Mass Index) is a widely used screening metric calculated from height and weight. It categorizes individuals as underweight, normal, overweight, or obese and helps identify potential weight-related health risks. The calculator supports metric and imperial units for global usability.
How to Use
- Enter your weight and select the unit (kg, lbs, or stone).
- Enter your height and select the unit (cm, m, or ft & in).
- Click Calculate BMI to get your result instantly.
- Review your BMI value, category, and healthy weight range shown in the results.
Formula Used
The metric formula divides weight in kilograms by the square of height in metres. The imperial variant uses a correction factor of 703 to convert pounds and inches to the same scale.
Understanding Your Results
Frequently Asked Questions
Is BMI accurate for athletes and muscular people?
No — BMI doesn't distinguish muscle from fat. A heavy-set rugby player can register as "obese" despite low body fat. For athletes, body fat percentage and waist-to-height ratio are better indicators.
What is a healthy BMI?
The WHO classifies 18.5–24.9 as healthy weight for adults globally. Underweight is below 18.5; overweight is 25–29.9; obese is 30 or above. Class II obesity (35+) and class III (40+) carry steeply higher health risks.
Does BMI vary by ethnicity?
Yes. Asian populations face cardio-metabolic risk at lower BMIs — many guidelines (China, India, Japan) shift the overweight threshold to 23 and obesity to 27.5. Pacific Islanders and people of African descent often have higher healthy ranges. Use ethnicity-specific cut-offs where available.
Is BMI the same for children?
No — children's BMI is interpreted via age- and sex-specific percentiles (BMI-for-age curves from WHO or CDC), not the adult thresholds. A child's BMI in the 85–95th percentile is overweight, above 95th is obese.
Important Note
BMI is a screening tool, not a diagnosis. It doesn't reflect muscle vs fat, age, sex, ethnicity, or body composition. Consult a doctor for a comprehensive health assessment.