Beginner
What do you say when people ask how good at chess you are ?

Do you have a link? I'd be interested to see. This is my FIDE card, I can't see any reference to a percentile.

I usually say that outside of chess.com, chess tournaments, and chess clubs, I have played over 80 games (lost count, really) in the past ten years and won all but one of them. On the other hand, at chess.com, and in tournaments, and at clubs, I lose all the time.
I also say that if chess were golf, I shoot about 90. How many people who play once every couple years shoot 90? None, that is how many. Yet 90 isn't all that good if you are a serious golfer.
So that is how I try to explain it.

Do you have a link? I'd be interested to see. This is my FIDE card, I can't see any reference to a percentile.
I'm pretty sure the underlying math was designed so that 2200 would be top 1%. Whether designed or not, it is very close to true for USCF ratings, and thus "national master" equates closely with "top 1%" of USCF players.
Also, chess.com provides a percentile ranking against your opponents here as well. You can find it in the mystats section of your profile. Yours is above 99%, so -- top 1% of the population here.
That doesn't quite answer your question about FIDE, but it should give you some ballpark idea. As it is often held the FIDE pool is a bit tougher, you are maybe only top 3% there.

I tell them Magnus Carlsen is scared -- he's ducking me. He won't return any of my calls or e-mails. He told someone I'm a forfølger, which I assume is Norwegian for unbeatable chess player.

@RCMorea, the FIDE pool is a lot tougher because only people who play proper tournaments get FIDE ratings. I doubt I'd even be top 5% on FIDE. Anyone can get a rating on Chess.com by clicking on a link from Facebook and playing 1 game.

With good reason, no one has ever asked me how "good" at chess I am.
I get asked at least once a week by passersby on the street.

You tell them that you are the greatest chess player of all time and that you once beat Garry Kasparov using nothing but a bishop and a piece of string.

I think I am an average player and find it difficult to answer to question when either a non-chess player asks me. It just seems difficult to answer when the asker has no knowledge of chess.
In the other situation when a rated chess players asks for my rating, that seems weird too. A rating is just a number but it seems the asker is trying to put a label on me. It just comes as someone asking how much money you make.
I think I am a decent player. I am not trying to falsely modest but I'm also not exceptional by any means.

If a non chess player asks and is really curious, I might tell them that I've won the city championship (a city of nearly half a million people) ten times, and yet I'm still not a master. That may give them an idea of how hard it is to become a master.
If it's just a casual conversation, I'll probably demur and say that I'm ok, or that I play chess competitively, but I'm not a master.

You tell them that you are the greatest chess player of all time and that you once beat Garry Kasparov using nothing but a bishop and a piece of string.
I can't wait to use that answer! Tomorrow I'm going to put a piece of string in my pocket, and spend the day walking around in the city, and every time a passerby asks me how good I am at chess, I'll tell them about me and Kasparov, and if they don't believe me, I'll show them the string, and then they'll be really impressed. Thanks for the idea!
Just say, "Not very good." For 99.99% of the people on earth, it will be true. And it's probable that the people who are very good don't get asked the question often.