Where does the 703 come from in BMI calculation?

If you use pounds in a BMI calculation, you must multiply the pounds by 703

You can see the formula here:

http://www.whathealth.com/bmi/formula.html Oh, I read the question wrong, why is 703 used? They must have figured out BMI for metric first and then divided the metric BMI by the number they got using imperial units, which would be 703. Then just multiply 703 into their formula.