I usually carry a Glock 27 w/a 9+1 magazine, plus one in the chamber, as well as when I'm outside the house have two 15 round G-22 mag's on me. I was taught to have at least one spare mag in case you have an issue caused by the magazine and added the second spare mag 'caues I was a Boy Scout. Plus, I believe in the thinking of "Two is One, One is None" that a lot of Preppers I've read about like to say.
Oh, and I have two 13 round G-23 mags and two 15 round G-22 mag's in the center console of my vee-hickle.
I don't set out to look for trouble, but you never know when trouble might find you.
"Zombies. Man, they freak me out."