Body Mass Index (BMI) Calculator
Understand your weight status with our free and easy-to-use BMI Calculator. Input your height and weight in metric or imperial units to get your BMI score and see which category you fall into. A helpful first step in assessing your health.
What is Body Mass Index (BMI)?
Body Mass Index (BMI) is a widely used measure to assess a person's weight relative to their height. It's calculated by dividing your weight in kilograms by the square of your height in meters (kg/m²). BMI provides a simple, inexpensive way to categorize weight status—underweight, healthy weight, overweight, or obese—and can be a useful screening tool for potential health risks associated with these categories.
While BMI is a helpful indicator for large populations, it's important to remember that it doesn't directly measure body fat. Factors like muscle mass, bone density, age, sex, and ethnicity can influence an individual's BMI and their corresponding health risk. For example, athletes with high muscle mass may have a high BMI but low body fat.
How to Use the BMI Calculator
- Select Units: Choose between "Metric (kg, cm)" or "Imperial (lb, ft, in)" units using the buttons at the top of the form.
- Enter Height:
- If using Metric: Enter your height in centimeters (cm).
- If using Imperial: Enter your height in feet (ft) and inches (in).
- Enter Weight:
- If using Metric: Enter your weight in kilograms (kg).
- If using Imperial: Enter your weight in pounds (lb).
- Calculate: Click the "Calculate BMI" button.
- View Results: Your calculated BMI value will be displayed, along with your corresponding BMI category (e.g., Normal weight, Overweight). The table below the result will also highlight your category.
Ensure you enter positive, realistic numbers for height and weight to get an accurate calculation. The calculator includes basic validation for common ranges.
Interpreting Your BMI Results
The BMI results are categorized as follows (based on World Health Organization classifications for adults):
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 to 24.9
- Overweight: BMI 25 to 29.9
- Obesity Class I: BMI 30 to 34.9
- Obesity Class II: BMI 35 to 39.9
- Obesity Class III (Morbid Obesity): BMI 40 or greater
Important Disclaimer: BMI is a screening tool and not a diagnostic measure of body fatness or overall health. It does not account for individual differences in body composition (muscle vs. fat), age, sex, or ethnicity. For example, muscular individuals may have a high BMI but not be overweight. Conversely, older adults with less muscle mass may have a normal BMI but still have excess body fat. This calculator is intended for adults aged 18 and over and is not suitable for children, teenagers, or pregnant/lactating women. Always consult with a healthcare professional for a comprehensive assessment of your health status and for personalized advice regarding your weight and well-being.
Limitations of BMI
While BMI is a convenient and widely used tool, it's essential to be aware of its limitations:
- Doesn't Distinguish Fat from Muscle: BMI can overestimate body fat in athletes and others with high muscle mass, or underestimate body fat in older persons and others who have lost muscle mass.
- Body Fat Distribution: BMI doesn't indicate where body fat is distributed. Fat around the abdomen (visceral fat) is generally considered more harmful than fat in other areas.
- Age and Sex Differences: For the same BMI, women tend to have more body fat than men. Older adults tend to have more body fat than younger adults with the same BMI. This standard calculator does not adjust for these factors.
- Ethnic Differences: The relationship between BMI, body fat percentage, and health risks can vary across different ethnic groups.
- Not for Children or Pregnant Women: Standard BMI charts are not appropriate for children, adolescents (who require age- and sex-specific percentile charts), or pregnant women (due to natural weight gain).
Therefore, BMI should be used as one part of a broader health assessment, alongside other measures like waist circumference, blood pressure, cholesterol levels, and lifestyle factors, under the guidance of a healthcare provider.
Frequently Asked Questions (FAQ)
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered to be in the healthy weight range. However, this can vary based on individual factors, so it's best to discuss your specific situation with a doctor.
How can I improve my BMI if it's too high or too low?
Improving your BMI generally involves lifestyle changes related to diet and physical activity. If your BMI is outside the healthy range, it's recommended to consult with a healthcare professional or a registered dietitian. They can help you develop a safe and effective plan tailored to your individual needs and health status.
Is the BMI calculation different for men and women?
The mathematical formula for calculating BMI is the same for adult men and women. However, the interpretation of BMI in terms of body fat percentage and health risks can differ slightly between sexes due to typical differences in body composition.
Does Toolixo store my height and weight data?
No, the BMI calculation is performed directly in your browser (client-side). Your height and weight data are not sent to our servers or stored by us. For more information, please see our Privacy Policy.