Body mass index, or BMI, is a way of measuring your body’s mass—a statistical measurement that gives an estimate of a healthy body weight based on the height of a person. Overall, it gives you and your doctor a good idea of how you stand weight-wise. In general, for an adult female (males have a bit higher BMI numbers), if you have a BMI less than 18.5, you are considered underweight; 18.5 to 24.9 means normal weight; 25 to 29.9 means overweight; and over 30 is considered obese. To determine your BMI, take your weight in pounds and your height in total inches. Then multiply your weight times 703, and divide that number by your height squared. For example, if you are 5 feet 4 inches tall (or 64 inches tall) and weigh 133, the calculation would be as follows: 133 × 703 = 93,449; 64 inches squared = 4,096; divide 93,449/4,096 = 22.83—a BMI in the normal range.