Just about any fitness magazine has a body mass index chart, and just about any health or fitness website has a BMI calculator. However, if for some reason you want to calculate your own BMI, you can do it quite easily if you know your height and weight.
Weigh yourself and jot down your weight in pounds. Find an accurate weight by weighing yourself first thing in the morning, before eating or getting dressed.
Calculate your height in inches. For instance, if you are 5 feet, 7 inches, multiply 5 by 12, and add 7, for a total of 67 inches.
Multiply your height in inches by itself, to get this number in units called "inches squared." Using the same example, a person 67 inches tall would calculate 67 in. x 67 in., for a result of 4,489 inches squared.
Divide your weight in pounds by your height in inches squared: If you weigh 130, you would calculate it like this: 130 / 4,489 = 0.029
Multiply that result by 703 to obtain your BMI. In this example, 0.029 x 703 = 20.4. This BMI falls in the normal range.