BMICalc is a Python console application which aims to show the body mass index of a person.

According to Wikipedia (http://en.wikipedia.org/wiki/Body_mass_index),

The body mass index (BMI), or Quetelet index, is a statistical measure of   
body weight based on a person's weight and height. Though it does not       
actually measure the percentage of body fat, it is used to estimate a       
healthy body weight based on a person's height. Due to its ease of          
measurement and calculation, it is the most widely used diagnostic tool to  
identify weight problems within a population, usually whether individuals   
are underweight, overweight  or obese. (...) Body mass index is defined as  
the individual's body weight divided by the square of his or her height.

BMICalc uses International System of Units (SI) to make the proper calculations. If you dislike this approach, feel free to implement calculations to the old imperial units system.