How to Calculate Ideal Body Weight Using BMI

Your BMI--body mass index--is a number that gives you an idea of how fit and healthy you are, roughly based on your ratio of weight to height. A high BMI corresponds to being overweight, and a low BMI corresponds to being underweight. According to the chart used by the NIH (Nat'l Inst. of Health), a healthy BMI is between 18.5 and 24.9.

If you want to calculate your range for a healthy body weight based on the BMI measurement, follow these steps below.

Difficulty:

Easy

Instructions

1. First, measure your height in inches, and call this number H. Remember that there are 12 inches per foot.

2. Next, square your height. That is, multiply your height by itself to find H².

   (Careful, this is not the same thing as multiplying by 2. For example, 5²= 25, not 10)

3. Now, to find the low end of the range for your ideal body weight, take H², multiply by 18.5, and divide by 703.

4. And to find the high end of the range for your ideal body weight, take H², multiply by 24.9, and divide by 703.

5. For example, if a man or woman is 68 inches tall (5'8"), then the low end is

   (18.5)(68²)/703 = 121.7 lbs, and the high end is

   (24.9)(68²)/703 = 163.8 lbs.

   So the range of healthy body weight for a 5'8" tall person is between 122 and 164 lbs, approximately.

6. Remember that BMI is only a rough guide of health. It does not measure percent body fat or lean muscle mass, both of which are very important indicators of health. Since muscle weighs more than fat, muscular and fit people may have a high BMI, even though they are not fat.