First off, yes, 40cf is 1132.67 liters. And yes, 1100L is quite a bit. Technically that's almost twice what you need to CTB(40 min @ 15LPM = 600L), but that's why I got it: I've got extra for things like flubbed attempts (six so far, but only three used any measure of gas) and for tweaking the flow rate up a bit to compensate for the fact I have an argon/CO2 regulator (cheap) instead of a dedicated N2 regulator (expensive).
As for gas tank sizes, they are notoriously non-standardized. Different companies develop their own sizes so that they can keep track of which are "their" tanks, when deciding whether to refill them, exchange them, etc., which makes the entire affair a damned nuisance. The only good news is that the valve threads are standardized, so at least any generic inert gas regulator will fit any tank of inert gas.
All of which is to say that you'll need to call your gas supplier and say something like, "I've been told I need about 1200 liters of nitrogen for my beer making project, but I don't know what size tank that would be." That phrasing is verbal prestidigitation: you're offhandedly mentioning the use (beer), and that you're a novice ("I've been told"), which diverts the salesman from ever putting much of his own thought into questioning you closely about why you need a specific amount; he can then focus on educating you about tank size --and the question of suicide never even comes up.
