BMI Calculator
Body Mass Index for adults
BMI Calculator
Enter your details to see your result.
Your BMI
Enter your details to see your result.
What is BMI?
Body Mass Index (BMI) is a simple screening measure that relates your weight to your height. It is calculated by dividing your weight in kilograms by the square of your height in metres (kg/m²). BMI is a useful, quick indicator for populations and individuals, but it does not distinguish muscle from fat or account for age, sex and body composition. Use it as a starting point, not a diagnosis.
WHO BMI categories
| Category | BMI range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obesity class I | 30.0 – 34.9 |
| Obesity class II | 35.0 – 39.9 |
| Obesity class III | 40.0 and above |
Frequently asked questions
Is this BMI calculator free?
Yes. It is completely free, requires no sign-up, and runs entirely in your browser — your data never leaves your device.
How is BMI calculated?
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). We handle the imperial conversion automatically.
Is BMI accurate for everyone?
BMI is a useful screening tool but not a diagnosis. It doesn't distinguish muscle from fat, so athletes and some body types may read higher. Always consult a professional for medical advice.
Does BMI work for children?
This calculator is designed for adults (18+). Children and teenagers use age- and sex-specific percentile charts instead.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered healthy according to the World Health Organization.