Yes, and in my glove box.. Usually just one but now that my EDC only holds 7 in a mag and I don't keep one in the the tube I have two spares in the glove box..
Never been one for extra mags on a belt clip, maybe if I were a LEO..
I usually don't carry a spare. But if I'm going into town, I do carry one in a jacket pocket.
__________________ If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen. ― Samuel Adams
It seems silly not to carry a spare mag. Compared to the gun a spare mag is not much trouble to include, there is always the possibility of a malfunction of your primary mag, and no one ever had a problem with having too many rounds of ammo.
Not carrying a spare mag does seem like an extremely silly proposition. They're easy to carry, so why not?
I don't carry one, and here's why: Since I was discharged from the Marines at the end of my contract, I've carried revolvers, and I'm a good shot. I sat down and looked at the info on hand. Most times, simply presenting a firearm ends many altercations. Those that have to fire, many times only have to fire 2-3 shots to end a bad situation, and it ends in either the bad guy running away, or injured. Less often than that, an armed citizen will actually fire their weapon until empty (that seems to be a thing for so called professionals). Very rarely does an armed citizen actually reload in an armed conflict. Even rarer still are the situations where an armed citizen has to reload AND reengage an attacker.
After looking at the data, and considering that speed loaders are bulky and a bit of a nuisance to carry, I decided that 6 shots of .357 magnum would be plenty for me ESPECIALLY considering my lifestyle. I frequent low crime areas, not because I'm scared, but because that's where I choose to live, work, and play. I don't go out. I really don't, I work and go home. I may have errands to run, but I generally just stay home. I no longer have a job that requires extensive traveling.
The risks considering my lifestyle and my home area make it so that I don't even really have to carry a gun. I just choose too. Better to have it and not need it, right?
Now that I carry a 1911, those magazines just beg to be carried. They plain and slender, no more obtrusive than a large pocket knife. So, I may drop an extra in my pocket if I take a road trip.