Always Two
I always carry a Sig P238 or my Colt Cobra revolver in my right front pocket. If something looks suspicious, but I don't want to overreact, I can just walk with my hand in my pocket and thus have quick and easy access while walking in and out of gas stations, through a parking lot, whatever.
I also always carry something with a little more firepower IWB, cross-draw, because it's difficult to access my pocket pistol while sitting down (such as while driving, or at my desk, or in a restaurant).
This is my standard dress, whether home or away.
It has never made sense to me when people say they carry two, or they carry something bigger, only if they "feel the need". The "need" can come up any time, any place. I live in the quiet suburbs, yet I have had bad guys on my back porch, trying to get in, while I was home. This is an experience that will change how you think about such things.
And finally, any incident that actually requires you to defend yourself or others, might just as easily be a situation where a backup is needed. Your primary could jam, you could drop it in a tussle with the bad guy(s), or who knows what. Carrying a backup is just as reasonable as carrying a higher capacity pistol instead of a lower capacity one.