BMI Calculator

Understand your body's health with our intuitive online calculator. Get accurate BMI and body composition insights instantly. This free online tool allows you to calculate your BMI quickly and accurately. No sign-up or installation required.

What is Body Mass Index (BMI)?

Body Mass Index (BMI) is a person's weight in kilograms divided by the square of their height in meters. It is an inexpensive and easy screening method for weight category—underweight, healthy weight, overweight, and obesity.

BMI does not measure body fat directly, but research has shown that BMI is moderately correlated with more direct measures of body fat obtained from skinfold thickness measurements, bioelectrical impedance, and other methods. Furthermore, BMI appears to be as strongly correlated with various metabolic and disease outcomes as are these more direct measures of body fatness.

BMI Categories

For adults 20 years old and older, BMI is interpreted using standard weight status categories. These categories are the same for men and women of all body types and ages.

Below 18.5: Underweight
18.5 – 24.9: Healthy Weight
25.0 – 29.9: Overweight
30.0 and Above: Obesity

Frequently Asked Questions

Is BMI an accurate indicator of health?

BMI is a useful screening tool for populations, but it has limitations at the individual level. It cannot distinguish between fat and muscle mass. Therefore, highly muscular athletes may have a high BMI indicating "overweight" or "obese," even though their body fat percentage is very low.

Does BMI apply to children and teens?

While the formula is the same, interpreting BMI for children and teens requires BMI percentiles. Because children's bodies change as they grow, and differ between boys and girls, their BMI must be compared against a growth chart of other children of the same age and sex.

Free Health Tool

BMI Calculator

What is Body Mass Index (BMI)?

BMI Categories

For adults 20 years old and older, BMI is interpreted using standard weight status categories. These categories are the same for men and women of all body types and ages.

Below 18.5: Underweight
18.5 – 24.9: Healthy Weight
25.0 – 29.9: Overweight
30.0 and Above: Obesity