[thaurelia]

You cannot compare ratings between these websites and FIDE for two reasons:

- they use different rating systems (Elo for FIDE, Glicko-2 for LiChess and afair, Glicko/Glicko-2 for chess.com)

- ELO / Glicko rating is calculated for a _player pool_. Which means it will never correspond between FIDE-registered players and chess websites because they don't have the same player base.

It has nothing to do with being “inflated” or “unrealistic”. The difference is “by design”

[zeven7]

I am not a chess player, but as a go player who has played on several different servers, all of that can be true and it can still be easier to compare progress relative to a real world association on one server vs another. ajkjk's point still makes sense to me.

[amalcon]

I think there's a third, bigger reason: FIDE rating is based on classical time controls. Nobody uses classical time controls online for various reasons. Even rapid is a somewhat different skill set than classical.

Of course these things are correlated, but e.g. there have been times in the world championship when one of the players thought about a position for 20+ minutes before making a move. That's hard to do, and requires very strong visualization skills.

[tehnub]

There are FIDE ratings for other time controls too. Here are the top blitz players for example: https://ratings.fide.com/top.phtml?list=men_blitz

[not_kurt_godel]

The bottom line is still that a chess.com rating will be more indicative of what a theoretical FIDE/USCF rating would be, and there's value in that, even if it's not rigorously tethered.

[thaurelia]

Comparison sites will give you ±150 Elo relative error (with I assume P=0.95).

150 Elo on levels below 2700 FIDE is almost night and day difference.

Chess.com ratings show nothing about theoretical FIDE ratings. Comparison tables have been built with data mining and lucky guesses, there's no quality difference between Chess.com <-> FIDE and LiChess <-> FIDE.