How long does it take to become a ghoul and how long does it take to become feral?

[CaptJ]

Thats an endless walker tho

An endless walker is a ghoul. I do remember something about ferals ghouls being used to scare people away from Necropolis. Admittedly, it isn't surprising that they turn feral compared to the mere fact that they survived the whole ordeal. However, Feral ghouls aren't particularly common in the classic Fallouts and they usually referred as just crazies rather than feral.

We have a canon answer but it is from Bethesda so I'm going to disregard it.

I think this is it. I can't go any further. I can feel it taking me. *growl* No, gotta keep it together a little longer. Oswald, I'm sorry. I've looked everywhere I could think, but there's no cure. What towns and outposts I could find said that we ghouls just go feral eventually, and there's nothing to be done. Maybe it was the misters. Held out... *moan* ...as long as I can. I know this isn't what you'd want but... I can't stand the thought of mindlessly attacking everyone around me, so I've decided to end it on my own terms. I don't know why it hasn't affected you the same, but if you've still held it together... I want you to move on. Leave Nuka-World. You can still make a life out there. It's not all as bad as we thought. I love you Oz.

 

[naossano]

It takes as long as the plot demands.
Some takes years to become ghouls, some mere seconds, some just die of radiation.
Some take years to become ferals, some mere seconds, some never become ferals.