How every move is classified
Most review tools show you a label and leave you to guess what it meant. These are the actual numbers this one uses.
Updated
Everything starts with winning chances
A raw engine evaluation is a poor measure of how bad a move was. Going from +9 to +7 is barely a scratch; going from +0.3 to −1.7 can lose the game. So the evaluation before and after each move is first converted into a winning percentage, how often the side to move would expect to win from that position, using the same logistic curve Lichess publishes.
The difference between those two percentages is the move's loss: how much winning chance it gave away. Every label below is a band of that one number.
The labels
| Label | Winning chance lost |
|---|---|
| Brilliant | ≤2 points, and a real material sacrifice (see below) |
| Great | ≤2 points, critical find that is not a sacrifice (see below) |
| Best | the engine's own move, losing 1 point or less |
| Only move | the engine's move, where the second-best was 12 or more points worse |
| Excellent | 2 points or less |
| Good | 5 points or less |
| Inaccuracy | 10 points or less |
| Mistake | 20 points or less |
| Blunder | more than 20 points |
Only move is worth explaining. It is not a better version of "best". It marks a position where there was exactly one road and you found it. If the second-best move would have cost you 12 or more percentage points, the position was on a knife edge, and playing the right move there deserves noting.
What makes a move brilliant
"Brilliant" is the label most likely to be handed out too freely, so it has four conditions and all of them must hold:
- You had a real choice. More than one legal move — a sole check escape does not count as brilliance.
- Real material is given up. At least 1.5 pawns' worth, measured after the engine's best continuation settles, so an ordinary trade where the material comes straight back does not qualify.
- The move is sound. It must cost 2 percentage points or less against the engine's choice, and leave you at 45% winning chance or better. A sacrifice that does not work is not brilliant.
- You were not already winning easily. If you were more than 3 pawns up, giving material back is slop, not brilliance.
That last condition uses material rather than winning chances. A forced mate already scores 100% before it is played, so a percentage-based guard would throw out every sacrifice that leads to mate, which is most of the good ones.
What makes a move great
Great is for critical finds that are not sacrifices. The move must be near the engine's choice (best, or at most 2 points of winning chance lost), and either:
- the second-best line was at least 8 points of winning chances worse, or
- your winning chances improved by at least 15 points from a losing or equal position (55% or less beforehand).
Brilliant is checked first, so a sound sacrifice never gets labelled Great.
How accuracy is calculated
Each move's loss is converted into a per-move accuracy score on a curve, and your accuracy for the game is the average of those scores across your own moves. The curve is steep at the start and flattens out: the difference between losing 0 and 5 percentage points matters far more than the difference between losing 40 and 45, because by then the damage is done.
This uses the same curve as Lichess, so accuracy figures here are comparable with the ones you see there.
Performance rating
Each side also gets a rating estimate for the quality of play in this game. roughly, the strength a player would need to have to play this well over a game of this length. It is a single game, so treat it as an indication rather than a verdict. Ten games tell you far more than one.