lol shit... yeah my math was off..... thats what i get for doing it in my head whilst taking my morning meds.
to elaborate, that formula is not 100% accurate as far as what the fan actually pushes, its just used to show the approximate volume of air that could be pushed through the fan under perfect condtions.
the /12 function is used to express cubic feet (CFM). dont divide by 12, and you get cubic inch