Recommendation 2 "How to" 
HOW TO CALCULATE YOUR BODY MASS INDEX OR BMI
BMI is your weight (in kilograms) over your height squared (in centimeters). Let’s calculate, however, using pounds and inches.
For instance, the BMI of a person who is 5’3" and weighs 125 lbs is calculated as follows:

2. Multiply the height in inches by
0.025 (the metric conversion factor) 
3. Square the answer from step 2 
4.Divide the answer from step 1 by the
answer from step 3 
The BMI for a person who is 5’3" and weighs 125 lbs is 22.7 or practically, 23. 
A healthy BMI ranges between 19 and 25.
Click here http://www.shapeup.org/sua/bmi/chart.htm to view a BMI chart.
Click here http://www.shapeup.org/sua/bmi/start.htm to calculate your BMI or here http://www.mayohealth.org/mayo/9602/htm/sb1.htm
The more sedentary your lifestyle, the closer your weight should be to the lower end of the recommended range. It is also important not to increase your weight significantly after age 18. Limit that weight gain to less than 11 pounds. The good news about this recommendation is that if you follow the exercise and dietary guidelines, it is much easier to maintain a healthy weight.
See Recommendation 2 Background for more on BMI.
BACK TO FOURTEEN RECOMMENDATIONS
Prepared 1998 by Bernadene Magnuson, Ph.D.
University of Idaho, Dept. of Food Science and Toxicology  EXTOXNET FAQ Team.