There are a great many threads already about this topic. You might have better luck with the search function.
It is a perennially popular topic. I think the answer will depend on the audience. If you are just a "shooter," you'll answer one way; if you are a "survivalist," that will not be enough. I lean toward the latter, but without taking it too seriously. But it has led me to be in a situation where the current shortages are only a minor irritation or interruption to my normal buying patterns.
Specifically, I try to keep 20k rounds of 22LR on hand. I haven't inventoried it lately, but I'm probably near or even a bit above that.
For handguns, I try to keep 1,000 rounds each of .38spl, .357 magnum, and 9 mm on hand. I reload these calibers, though, and try to keep at least 5k each of small and large pistol primers on hand, and have enough brass to reload indefinitely. I'm also sitting pretty with bullets and powder for these calibers.
For centerfire rifle cartridges, for .223 I like to keep on the far side of 5k, since that is fired in a semi-auto with 30 round mags. For bolt and lever actions, 1k for each rifle, whatever the caliber. I'm tooling up to reload .223 and .308. I have all the components I need to reload .223 for some time. I just began purchasing brass and bullets for .308, but I'll wait and see if supply and price ease before stocking up on primers and powder.
So even if the S-never-HTF, following these guidelines meant that when the current crisis hit, I was already in good enough shape to weather it.