BMI.

The Body Mass Index (BMI) Calculator can be used to calculate your BMI va
lue and weight status while taking your age into consideration. Use the 
"metric units" tab if you are more comfortable with the international 
standard metric units. The referenced weight range and calculation formula 
is listed below.

Reference
Your BMI is a measurement of your body weight based on your height and
weight. Although your BMI does not actually "measure" your percentage of 
body fat, it is a useful tool to estimate a healthy body weight based on 
your height. Due to its ease of measurement and calculation, it is the most 
widely used diagnostic indicator to identify a person's optimal weight 
depending on his height. Your BMI "number" will inform you if you are 
underweight, of normal weight, overweight, or obese. However, due to 
the wide variety of body types, the distribution of muscle and bone mass, 
etc., it is not appropriate to use this as the only or final indication for 
diagnosis.


Body Mass Index Formula.


The formulas to calculate BMI based on two of the most commonly used unit systems:

BMI = weight(kg)/height2(m2)   (Metric Units)
BMI = 703·weight(lb)/height2(in2) (U.S. Units)