Here is the way your BMI is calculated. I think it's pretty interesting myself. There are a few links at the bottom as well if you want some more reading.

--------------- Calculating BMI ---------------

Weight pounds

----------------------------- x 703

height (inches) x height (inches)

Here's an excel forumula:

=((pounds(inches*inches))*703)

Here's my stats in the formulas:

270.5

---------- x 703 = 32.9

76 x 76

=((270.5/(76*76))*703)

Now something to bear in mind.

BMI is based on 'averages' for a 'normal' human being. Muscle mass skews the calculations. Here's an example.

I have a friend, he is 5 feet 4 inches tall. He weighs 240 pounds.

So that is:

((240/(64*64))*703 = 41.2

Therefor my friend is morbidly obese and qualifies for weight loss surgery.

Now here comes the catch.

My friend has a bodyfat of 6%. He is entirely lean muscle (and terrifying) but this clearly shows that the BMI calculation is flawed.

You should always get a body fat assessment to truly validate your BMI classification!

--------------- BMI Calculator Links ---------------

(Provided by the Department of Health and Human Services, Centers for Disease Control Prevention)

http://www.cdc.gov/nccdphp/dnpa/bmi/...calculator.htm

I also have used:

http://www.bmi-calculator.net/