What is BMI?
BMI stands for Body Mass Index. It is a widely used formula that compares a person’s weight to their height. The result provides a general estimate that can help classify weight status into standard categories such as underweight, normal weight, overweight, and obesity.
A BMI calculator is useful because it gives a quick and simple number that can be used as a basic screening tool. It is commonly used in public health, fitness, and general health education.
How BMI is calculated
In metric units, the formula is:
BMI = weight (kg) ÷ height (m)²
In imperial units, the formula is:
BMI = 703 × weight (lb) ÷ height (in)²
BMI categories
The standard BMI categories for adults are commonly interpreted as follows:
| BMI Range |
Category |
| Below 18.5 |
Underweight |
| 18.5 to 24.9 |
Normal weight |
| 25.0 to 29.9 |
Overweight |
| 30.0 and above |
Obesity |
These ranges are intended for general adult screening. A healthcare professional may consider many other factors when evaluating health, body composition, or risk.
How to use this BMI Calculator
- Select either metric or imperial units.
- Enter your weight and height.
- Your BMI will appear automatically.
- Review the category shown below the result.
This tool is designed to be fast, simple, and easy to use on desktop or mobile devices.
Limitations of BMI
BMI is useful, but it has limitations. It does not directly measure body fat, muscle mass, bone density, or fat distribution. For example, an athlete with high muscle mass may have a high BMI without having excess body fat.
Because of this, BMI should be viewed as a screening metric rather than a full health diagnosis.
Frequently asked questions
Is BMI accurate?
BMI is useful as a general estimate, but it is not a direct measure of body fat or overall health. It works best as a basic screening tool.
Can I use this calculator on mobile?
Yes. The calculator is fully responsive and works on phones, tablets, and desktop devices.
Does this BMI Calculator store my data?
No. This page does not require an account or login, and the values you enter are calculated directly in your browser.
Should children use the same BMI categories?
No. BMI interpretation for children and teens is different and usually depends on age and sex-specific growth charts.