BMI Calculator
Calculate your Body Mass Index and understand your health
BMI Categories (WHO Standard)
| Category | BMI Range | Health Risk |
|---|---|---|
| Underweight | < 18.5 | Possible nutritional deficiency |
| Normal | 18.5 – 24.9 | Low risk |
| Overweight | 25.0 – 29.9 | Moderate risk |
| Obese Class I | 30.0 – 34.9 | High risk |
| Obese Class II | 35.0 – 39.9 | Very high risk |
| Obese Class III | ≥ 40.0 | Extremely high risk |
Free Online BMI Calculator – Check Your Body Mass Index
Understanding your body weight in relation to your height is one of the most important steps toward a healthier lifestyle. Our professional BMI Calculator provides instant, medically recognized results based on the World Health Organization (WHO) standards, along with helpful insights like your healthy weight range, BMI Prime, and a visual scale for easy interpretation.
What Is BMI?
BMI, or Body Mass Index, is a widely used health screening metric that evaluates whether a person has a healthy body weight relative to their height. It is calculated using a simple formula: BMI = Weight (kg) ÷ Height (m)². The resulting number places you into one of several categories defined by the WHO: Underweight, Normal, Overweight, or Obese (Class I, II, or III). While BMI is not a direct measure of body fat, it serves as a reliable initial indicator of potential weight-related health risks for the general adult population.
How to Use the BMI Calculator (Step-by-Step Guide)
Getting your BMI result takes just a few seconds with our intuitive interface:
- Select Your Unit System: Toggle between Metric (kilograms and centimeters) or Imperial (pounds and feet/inches) using the switcher at the top.
- Enter Your Weight: Type your body weight into the weight field.
- Enter Your Height: Input your height. If using Imperial, enter feet and inches separately in the two provided fields.
- Click "Calculate BMI": Your BMI score, category, health risk level, healthy weight range, and a visual color-coded scale will appear instantly.
Why Should You Use This Tool? (Benefits)
- Instant Health Insight: Get your BMI category and health risk level in seconds — no manual math required.
- Visual BMI Scale: A color-coded gradient bar with a moving marker shows exactly where your BMI falls among the WHO categories, making it easy to understand at a glance.
- Healthy Weight Range: See the specific weight range you should aim for based on your height, so you have a clear, actionable target.
- Dual Unit Support: Works seamlessly with both Metric (kg/cm) and Imperial (lb/ft/in), so you can use whichever system you're comfortable with.
- Advanced Metrics: Beyond basic BMI, we also calculate your BMI Prime (ratio to upper normal BMI) and Ponderal Index for deeper insight.
- 100% Private: All calculations run in your browser. We never store or transmit your health data.
Who Is This Tool For?
- Health-Conscious Individuals: Anyone wanting a quick snapshot of where their weight stands relative to their height.
- Fitness Enthusiasts: To track BMI changes over time as part of a weight management or fitness program.
- Healthcare Professionals: As a quick reference tool for initial patient screenings and consultations.
- Nutritionists & Dietitians: To provide clients with a starting-point metric for dietary and lifestyle planning.
- Students & Researchers: For academic projects related to public health, nutrition science, and human biology.
Frequently Asked Questions
BMI stands for Body Mass Index. It is a numerical value calculated from your weight and height that categorizes you as underweight, normal weight, overweight, or obese. The formula is: BMI = weight (kg) / height (m)².
BMI is calculated by dividing your body weight in kilograms by the square of your height in meters. For example, if you weigh 70 kg and are 1.75 m tall, your BMI = 70 / (1.75 × 1.75) = 22.86.
The World Health Organization (WHO) defines BMI categories as: Underweight (BMI < 18.5), Normal weight (BMI 18.5–24.9), Overweight (BMI 25–29.9), Obese Class I (BMI 30–34.9), Obese Class II (BMI 35–39.9), and Obese Class III (BMI ≥ 40).
BMI is a useful screening tool for the general population, but it has limitations. It does not distinguish between muscle mass and fat mass, so athletes or muscular individuals may have a high BMI without being overweight. It also does not account for age, gender, or body composition.
Yes! Our BMI Calculator supports both unit systems. You can enter your weight in kilograms or pounds and your height in centimeters or feet/inches. Simply toggle the unit switch to change between Metric and Imperial.
A healthy BMI range is generally considered to be between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health problems. However, individual health depends on many factors beyond BMI.
For children and teens (ages 2-19), BMI is calculated the same way but interpreted using age- and sex-specific percentiles rather than fixed categories. Our calculator is designed for adults aged 20 and older.
A BMI in the overweight or obese range is associated with increased risks of heart disease, type 2 diabetes, high blood pressure, stroke, certain cancers, sleep apnea, and joint problems. Maintaining a healthy BMI can significantly reduce these risks.
No. All calculations are performed locally in your web browser using JavaScript. We do not store, collect, or transmit any of your personal health data to our servers.
Yes, this BMI Calculator is 100% free with no registration, no hidden fees, and no daily usage limits.