Question:
How exactly are BMI's calculated?

I am wondering why so many sites come up with different BMI's every time I type in the same information. What is the EXACT formula for calculating a BMI? Thanks    — Kay A. (posted on February 14, 2000)

February 14, 2000
There are several formulas to calculate BMI. Some are very complicated, especially for the math challenged!! :D But I think you may find the variations because some of the different sites which will calculate your BMI automatically do not allow for fractional heights. ie, 5-4, rather than 5-4 1/2 so the rounding off may be one reason for the differences. I have seen all the formulas but I am going to post the one that is the most easy to use. FORMULA for BMI made simple!!! MULTIPLY YOUR WEIGHT BY 703, THEN MULTIPLY YOUR HEIGHT (in inches)-BY ITSELF. FINALLY, DIVIDE THE FIRST NUMBER BY THE SECOND NUMBER. there's your BMI and all you have to do is multiply and divide regular numbers, not kilograms, squared numbers etc. Very simple and allows for the in between heights!!
   — Fran B.