A measure of body weight relative to height. BMI is a measure that is often used to determine if a person is at a healthy weight, overweight, or obese, and whether a person's health is at risk due to his or her weight.To figure out BMI, use the following formula:
BMI = weight (lb) / [height (in)]2x 703.
Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703.For adults 20 years of age and older, a BMI of 18.5 to 24.9 is considered healthy. A person with a BMI of 25 to 29.9 is considered overweight, and a person with a BMI of 30 or more is considered obese.Note: BMI is used as a screening tool to identify possible weight problems for adults. However, BMI is not a diagnostic tool. For example, if a person has a high BMI, a health care provider would need to perform further assessments to determine if the excess weight is a health risk. These assessments might include evaluations of diet, physical activity, family history, blood tests and other appropriate health screenings.It is important to remember that although BMI correlates with the amount of body fat, BMI does not directly measure body fat. As a result, some people, such as athletes, may have a BMI that identifies them as overweight even though they do not have excess body fat.