ChessGrader / Chess accuracy calculator
Chess accuracy calculator: check any game free
Enter a Chess.com or Lichess username, or paste a PGN. ChessGrader calculates both players' accuracy and shows the moves that raised or ruined the score. Free, unlimited, no signup.
What the accuracy score tells you
Chess accuracy measures how much winning chance your moves preserved compared with the engine's preferred moves. A move that changes nothing costs almost no accuracy. A move that turns a winning position into a loss costs a lot.
The number needs context. Forced sequences and easy winning positions often produce high scores. Complicated, balanced games produce lower scores because more moves carry real consequences. Read the score beside the position, not as a rating of your intelligence or talent.
A practical guide to chess accuracy
| Accuracy | Useful reading |
|---|---|
| 90%+ | Very clean, or a game with many obvious and forced moves |
| 80–90% | Strong for most club players, especially in a balanced game |
| 70–80% | Solid, usually with a few mistakes worth reviewing |
| Below 70% | A messy game, a major blunder, or a difficult position |
These ranges are guideposts, not universal standards. Our accuracy guide breaks them down by rating and explains why a lower score can come from a better, harder game.
What ChessGrader calculates with it
The calculator opens the complete game review, so you also get:
- Every move graded from Brilliant to Blunder
- An evaluation graph showing where the game changed
- Average centipawn loss for each player
- An estimated single-game performance rating
- Plain-English explanations and drills for important mistakes
Chess.com's exact accuracy formula is private. ChessGrader uses a published, CAPS2-inspired approximation based on expected-points loss. The engine settings, safeguards, and limits are documented in the ChessGrader methodology.
Frequently asked questions
How do I calculate accuracy for a Chess.com game?
Choose Chess.com above and enter the public username. Pick a finished game from the archive and ChessGrader calculates both players’ accuracy during the full review. No Chess.com login or password is needed.
Can I calculate chess accuracy from a PGN?
Yes. Choose Paste PGN, paste one complete standard game, and start the analysis. The PGN stays in your browser and is not uploaded to a ChessGrader server.
Is 90% chess accuracy always good?
It is a high score, but not always evidence of a difficult or exceptional game. Short wins, forced sequences, and positions where many moves win can all produce 90% or more. The mistakes and turning points explain more than the headline number.
Why is my ChessGrader accuracy different from Chess.com?
The sites use different search settings and formulas. Chess.com keeps its exact CAPS2 calculation private. ChessGrader publishes its own CAPS2-inspired approximation, so the same game can receive different scores.
Does a high accuracy score prove someone cheated?
No. One high-accuracy game proves nothing. Honest players regularly score above 90% in short, forced, or one-sided games. Fair-play detection requires patterns across many games plus information that a public game review does not have.