BMI Calculator
Calculate your Body Mass Index to check whether your weight falls within a healthy range. Supports both metric (kg/cm) and imperial (lbs/ft) units.
For adults aged 20 and older - based on WHO classification
Calculate Your BMI
Enter your weight in pounds
Feet portion of your height
Inches portion (0-11)
BMI Categories Reference
| Category | BMI Range | Risk Level |
|---|---|---|
| Severe Underweight | Below 16.0 | High |
| Underweight | 16.0 - 18.4 | Moderate |
| Normal Weight | 18.5 - 24.9 | Low |
| Overweight | 25.0 - 29.9 | Moderate |
| Obese (Class I) | 30.0 - 34.9 | High |
| Obese (Class II) | 35.0 - 39.9 | Very High |
| Obese (Class III) | 40.0 and above | Extremely High |
Based on World Health Organization (WHO) classification for adults aged 20 and older.
How to Use This BMI Calculator
Choose Your Units
Select imperial (lbs, feet/inches) or metric (kg, cm) using the toggle switch at the top of the calculator.
Enter Your Measurements
Type in your weight and height. For imperial, enter feet and inches separately. For metric, enter kilograms and centimeters.
View Your Results
Click Calculate BMI to see your BMI value, category classification, a visual scale showing where you fall, and health risk level.
How BMI Is Calculated
BMI = weight(kg) / height(m)^2Body Mass Index is a simple ratio of weight to height. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and remains one of the most widely used screening tools for categorizing weight status.
Metric: BMI = weight(kg) / [height(m)]^2Imperial: BMI = [weight(lbs) x 703] / [height(in)]^2Key details about the BMI formula:
- Height is squared, which means height has a greater proportional effect on BMI than weight does
- The 703 multiplier in the imperial formula converts the result to match the metric scale (kg/m^2)
- BMI does not measure body fat directly - it is a proxy based on weight-to-height ratio
- The same thresholds apply regardless of sex for adults, though health risks may differ between men and women at the same BMI
While BMI is a useful population-level screening tool, individual health assessments should include additional factors such as waist circumference, body composition, blood pressure, cholesterol levels, and family medical history.
Frequently Asked Questions
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by the square of your height in meters. The formula is: BMI = weight(kg) / height(m)^2. For imperial units, the formula is: BMI = (weight in lbs x 703) / (height in inches)^2. A BMI between 18.5 and 24.9 is generally considered a healthy range for adults.
What are the BMI categories?
The World Health Organization defines these BMI categories for adults: Underweight is below 18.5, Normal Weight is 18.5 to 24.9, Overweight is 25.0 to 29.9, and Obese is 30.0 and above. Obesity is further divided into Class I (30-34.9), Class II (35-39.9), and Class III (40+), sometimes called severe or morbid obesity.
Is BMI accurate for everyone?
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 very muscular individuals may have a high BMI despite low body fat. It also does not account for age, sex, bone density, or fat distribution. For a more complete health assessment, consult a healthcare provider who can consider additional measurements like waist circumference and body fat percentage.
What is a healthy BMI range?
A BMI between 18.5 and 24.9 is considered a healthy (normal) weight for most adults. However, optimal BMI can vary by age, sex, and ethnicity. Some research suggests that a BMI between 20 and 25 may be associated with the lowest health risks. Maintaining a healthy BMI is associated with lower risk of heart disease, type 2 diabetes, high blood pressure, and certain cancers.
Does BMI apply to children and teenagers?
BMI is calculated the same way for children and teens, but the interpretation is different. For people aged 2 to 19, BMI is expressed as a percentile relative to other children of the same age and sex (BMI-for-age). A percentile between the 5th and 85th is considered healthy weight. This calculator is designed for adults aged 20 and older.
Important Disclaimer
This BMI calculator is provided for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. BMI is a screening tool and does not directly measure body fat percentage or overall health. It may overestimate body fat in athletes and muscular individuals, and underestimate it in older adults or those with low muscle mass. Always consult a qualified healthcare provider for personalized health assessments and recommendations.