BMI Calculator
Use this BMI calculator to quickly determine your body mass index based on your height and weight. BMI is a simple screening tool used to estimate whether you fall within a healthy weight range.
Your Measurements
Your BMI
Enter your height and weight to calculate BMI.
What Is BMI?
Body Mass Index (BMI) is a numerical measure of body fat based on height and weight. Developed in the 1830s by Belgian mathematician Adolphe Quetelet, it is now the most widely used screening tool for identifying potential weight-related health risks in adults. The formula is simple: divide your weight in kilograms by the square of your height in meters (BMI = kg/m²). In US customary units, the adjusted formula is BMI = 703 × lb / in².
BMI is not a diagnostic tool — it cannot measure body fat percentage directly — but it is a quick, low-cost first step used by clinicians to identify patients who may need further assessment.
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
How to Use This Calculator
- Select your preferred units — inches/pounds (US) or centimeters/kilograms (metric).
- Enter your height in the height field.
- Enter your current body weight in the weight field.
- Click Calculate to see your BMI score and the corresponding weight category.
Frequently Asked Questions
Is BMI an accurate measure of body fat?
BMI is a useful screening tool but has well-known limitations. It does not directly measure body fat. A muscular athlete may have a high BMI without excess fat, while an elderly person with low muscle mass may have a "normal" BMI but still carry too much fat. Always interpret BMI alongside other health indicators such as waist circumference and blood pressure.
What is a healthy BMI for adults?
For most adults, a BMI between 18.5 and 24.9 is considered healthy by the World Health Organization (WHO). Some health organisations use slightly different thresholds for people of Asian descent, where health risks can appear at lower BMI values.
Can I use this calculator for children?
No — this calculator is designed for adults 18 and older. For children and teenagers (ages 2–19), BMI is interpreted using age- and sex-specific growth charts called BMI-for-age percentiles, which account for normal changes in body fat as children grow.
What should I do if my BMI is outside the healthy range?
Consult a healthcare professional before making significant dietary or exercise changes. BMI alone is not a diagnosis. Your doctor will review other factors — blood work, blood pressure, lifestyle habits — to give a complete picture of your health and recommend next steps.