Calculate Body Mass Index from height and weight.
BMI is a useful screening measure, but it does not directly tell how much body fat, muscle, or bone mass a person has.
Body Mass Index compares body weight with height to place the result into a broad screening category. It is widely used because it is simple, quick, and easy to calculate.
Body Mass Index, usually shortened to BMI, is a quick way to compare body weight with height. It is commonly used as a screening tool to place adults into broad categories such as underweight, normal weight, overweight, or obesity.
A BMI calculator is useful because it gives an instant result from a small amount of information. That makes it a popular starting point for general health and fitness tracking.
BMI is meant to provide a simple population-level screening measure. It can highlight whether body weight is broadly low, typical, or high relative to height, and it is often used in public health, clinical screening, and general health education.
It is helpful as a first-pass indicator, but it is not a full assessment of health, body composition, or disease risk on its own.
The calculation uses only height and weight.
This calculator accepts either metric or imperial units and returns the BMI value together with the matching category.
| Category | BMI Range | General Interpretation |
|---|---|---|
| Underweight | Less than 18.5 | Below the usual adult range |
| Normal weight | 18.5 – 24.9 | Within the usual adult range |
| Overweight | 25.0 – 29.9 | Above the usual adult range |
| Obesity | 30.0 and above | Higher BMI screening category |
BMI does not measure body fat directly. It also does not account for muscle mass, frame size, bone density, or where body fat is stored. That means it can sometimes misclassify individuals.
This is why BMI is usually most useful when combined with other information such as waist measures, fitness level, health history, and clinical judgement.
Even with its limitations, BMI remains useful because it is simple, quick, and widely understood. It can help with:
Standard adult BMI categories are not usually applied in the same way to children and teenagers. Younger age groups are normally assessed using age- and sex-specific percentile approaches because growth and development patterns vary.
BMI stands for Body Mass Index. It is a screening measure that compares weight to height and places the result into a broad category such as underweight, normal weight, overweight, or obesity.
In metric units, BMI is weight in kilograms divided by height in metres squared. In imperial units, BMI is weight in pounds divided by height in inches squared, then multiplied by 703.
No. BMI is useful as a broad screening tool, but it does not directly measure body fat, muscle mass, bone density, or fat distribution.
Yes. A muscular person may have a higher BMI without having excess body fat, which is one reason BMI should not be treated as a full health assessment on its own.
No. Children and teenagers are usually assessed with age- and sex-specific BMI percentile approaches rather than the standard adult category cutoffs.
For connected health calculations, see the Fasting Calculator, Steps to Miles Calculator, and Protein Calculator.
BMI is best treated as a useful screening measure rather than a full diagnosis. It can be a practical starting point, but a broader view of health usually includes body composition, activity, diet, lifestyle, and clinical context.