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What is BMI?

Body Mass Index or BMI (wt/ht²), based on an individual's height and weight, is a helpful indicator of obesity and underweight in adults.¹

BMI English Formula

BMI =
[Weight in pounds ÷ Height in inches ÷ Height in inches] x 703

Click here for our online BMI Calculator

Example
A person weighing 210 pounds and 6 feet tall would have a BMI = 210 pounds divided by 72 inches divided by 72 inches multiplied by 703 = 28.5

BMI compares well to body fat but cannot be interpreted as a certain percentage of body fat. The relation between fatness and BMI is influenced by age and gender. For example, women are more likely to have a higher percent of body fat than men for the same BMI. At the same BMI, older people have more body fat than younger adults.²

BMI is used to screen and monitor a population to detect risk of health or nutritional disorders. In an individual, other data must be used to determine if a high BMI is associated with increased risk of disease and death for that person. BMI alone is not diagnostic. ³

How does BMI relate to health among adults?

A healthy BMI for adults is between 18.5 and 24.9. BMI ranges are based on the effect body weight has on disease and death. ⁴ 

A high BMI is predictive of death from cardiovascular disease. Diabetes, cancer, high blood pressure and osteoarthritis are also common consequences of overweight and obesity in adults. Obesity itself is a strong risk factor for premature death. ⁵

BMI Cutpoints for Adults

We interpret BMI values for adults with one fixed number, regardless of age or sex, using the following guidelines:

References

1. Garrow JS and Webster J. Quetelet’s index (W/H²) as a measure of fatness. International Journal of Obesity 1985;9:147-153.

2. Gallagher D, et al. How useful is BMI for comparison of body fatness across age, sex and ethnic groups? American Journal of Epidemiology 1996;143:228-239.

3. Willett W, et al. Guidelines for healthy weight. New England Journal of Medicine 1999;341:427-434.

4. World Health Organization. Physical status: The use and interpretation of anthropometry. Geneva, Switzerland: World Health Organization 1995. WHO Technical Report Series.

5. Calle EE, et al. BMI and mortality in a prospective cohort of U.S. adults. New England Journal of Medicine 1999;341:1097-1105.