A measure of "fatness" used in medicine and health. The BMI is equal to a person's mass ("weight") M (in kilograms) divided by the square of his or her height H (in meters): BMI = M/H2. If measurements are made in traditional English units, the equivalent formula is BMI = 703.07 M/H2, where M is measured in pounds and H in inches. In the U.S., a person with a BMI less than 20 is considered underweight, a person with a BMI of 25 or more is considered overweight, and a person with a BMI of 30 or more is considered obese. (These figures are for adults. Doctors also keep in mind that women's BMI measures are normally lower than those of men.)