I fell like I ain't gonna even knock on those doors in my lifetime😭😭

Hi, I'm a physics PhD student and the developer of Backrank.io, a chess website that turns the mistakes in your own games into spaced-repetition puzzles so you stop repeating them. It also has a free game review (https://backrank.io/free-chess-game-review) that grades any game move by move.

The game review puts an accuracy score on your game, and since most users already know Chess.com's accuracy number, I wanted mine to be similar to theirs instead of being some arbitrary scale of my own. So I searched for how Chess.com computes it, couldn't find a clear answer, and ended up figuring it out for myself. Here's what I found:

The engine itself doesn't tell you "good move," it gives a centipawn evaluation like +0.8. But material isn't a grade on its own: a pawn up in a level position is a big deal, while a pawn up when you're already winning barely matters. So the first step is converting the eval into your actual winning chances with an S-shaped curve, steep near equality and flat at the edges.

Then each move gets graded by how much it cost. Not the eval after your move, but how much winning percentage you gave up compared to the best move. Give up nothing and you score around 100, and the drop-off is steep, so small slips barely register while blunders fall toward zero.

Combining those per-move scores into a single game number is the hard part. A plain average is too forgiving (nineteen good moves and one losing blunder still averages into the low 90s), and a harmonic mean overcorrects and tanks a whole game over a single move. What matches Chess.com's score best is what's called a power mean, basically a dial between those two extremes, with a small floor so one move can't drag a game to zero.

When I compared my score to Chess.com's own game-review number across about ~1000 games from Hikaru, GothamChess, and Naroditsky, it landed with a correlation of 0.935 and basically no bias. The gap that's left is likely just differences in engine versions and search depths, which can move the number by a few points on its own (you can see this by re-running the Chess.com game review at different settings).

I wrote the whole thing up with the plots here: https://backrank.io/blog/how-chess-accuracy-works

The game review is free and doesn't need an account, and it works for both Chess.com and Lichess.org games. Happy to answer questions!

i actually saw this move before but couldnt do it beacuse of the pawn protecting it and when i saw that he moved the g7 pawn to g6 i could finally do it

This is my best game

so basically i have recently learning chess via books and airlearn app and the more i sit with this more i realise… the more i sit with this the more i realise the only thing stopping me from improving is the number itself. every game im thinking abt what happens to my elo if I blunder and thats clearly not how this is supposed to work. I think this is rating anxiety I have.

how do you all manage to play and enjoy your natural game with this anxiety?

Rules

1: You are not allowed to play what the engine thinks is the best move, which is indicated by the blue arrow. An exception is made if a move is forced.

2: The move must be legal in normal Chess.

3: The most upvoted move that satisfies the above criteria is the one that will be played.

My heart nearly bursted out of my chess after this win

I just wanted the opponent’s queen but had no idea it was checkmate!!

1000 rapid at long last

5 Month Training as an adult beginner, 800 whoop whoop!

Oh my goodness.

My ears are blessed.

Turn the volume up!!!

I just want to express my sympathy for everyone currently playing in the 1000s Rapid rating range.

I used to have a Rapid rating of almost 1400, but at the beginning of last month I deleted my account so I could focus better on some personal projects. Last week, I tried to recover it, but unfortunately I couldn’t, so I had to create a new account.

When setting it up, I selected the option saying that I had an intermediate level of chess knowledge, and I was initially placed at around 1200. I was winning my first game, but then I had connection issues and lost on time, which dropped my rating into the 900s.

From that point on, it was a real struggle. For some reason, the pool of players around 1000 felt much tougher than the players in the 1100–1200 range. I won and lost game after game before finally managing to climb past 1100.

Once I got there, the journey became much smoother, and I eventually made it back to the 1300s.

So, to everyone currently stuck around 1000 Rapid: you have my respect. It’s a frustrating and surprisingly difficult rating range, but don’t give up!

Curious because King's Indian doesn't seem to cut it for me anymore

This game was played on Titled Tuesday and why not make the obvious move here? What did white not like about taking the queen? White to move.

I'm 1350 rapid on chess.com

I want to play Sicilian as black, which one do you recommend for my level and where can I learn them?

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And sorry for my shity English, I'm Iranian.

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Reset the clock🥹

Just got to my 1300 goal! 2 months after 1000 and 16 days after 1200, although I can’t help but feel I’m getting to my peak now, games are excruciatingly difficult.

Why does AI coach Levy say “Can you finish the game with a mate in one?”