How much carry ammo is enough?

i carry at least one spare mag, for more even weight, or else i get back pain (2.5lb USP). extra rounds are nice but no pain is +

I carry 1 round for my LCP .380. That way if I run into 10+ bad guys, it gives the remaining a fighting chance.

my EDC setups allow for an extra mag, they are comfortable and light weight.

i would think that having a backup mag is important for all kinds of reasons,