how to calculate a standard drink from the alcohol percentage?
It is easier to define the standard drink by volume as you won't have to switch between concentrations by volume (as is normal in most drinks) and grams. 

This is probably where your recollection of moles comes in as somewhere in this morass of units they get involved.

14 grams of alcohol is 17.7 ml

so 30% alcohol (many spirits) to get to a 100% you need to add another 70/100 ths of volume.

(17.7/30)*100 = 59 ml of drink which just so happens to be two fluid ounces for our american viewers. 

or, slightly less intuitive but easier to use: 

the volume of your drink = 17.7 / (the concentration or your drink /100)

Now if you want to use the "proof" of your drink as a unit of volume I'll need a drink first.