What does the evaluation mean in chess? +1.5, -0.8 and M3 explained
The number next to the board is how much better one side is, in pawns. Here’s how to read +1.5, -0.8 and M3, and when not to trust it.
The evaluation is the engine’s estimate of who is better and by how much. A plus sign means White is better, a minus sign means Black is, and the number is roughly how many pawns the advantage is worth. M followed by a number means someone has a forced mate.
What does +1.5 mean in chess?
White is better by about a pawn and a half. White may be a pawn and a half up in material, but not necessarily. The engine also counts things like a safer king, more active pieces or a pawn close to queening, and puts them in the same unit.
So +1.5 with equal material means White’s position is worth about a pawn and a half more, even though nothing has been taken yet.
What does a minus number mean?
The same thing for Black. -0.8 means Black is better by a bit under a pawn. The evaluation is always given from White’s side, whoever is to move and whichever way the board is turned.
How do you read the numbers?
Treat these as rough guides. Every engine, and every version of it, reads a little differently.
| Evaluation | What it usually means |
|---|---|
| 0.00 to ±0.2 | Equal, or as good as equal |
| ±0.3 to ±0.7 | A small edge, nothing decisive |
| ±0.8 to ±1.5 | A clear advantage that still has to be converted |
| ±1.6 to ±3 | Close to winning, if the stronger side plays well |
| More than ±3 | Winning for the engine, and usually for a human too |
| M3 or -M3 | Mate in three, for White or for Black |
What does M mean on the evaluation bar?
M means mate. M3 is a forced mate in three moves for White, and -M3 the same for Black. Once the engine sees a forced mate, it stops counting in pawns and shows the number of moves instead. When the mate is on the board, the bar fills completely.
Is the evaluation the same as a win percentage?
No, but the two are linked. Since version 15.1, Stockfish scales its numbers so that +1.00 means about a 50 % chance of winning for the stronger side against an equal opponent, with most of the rest being draws. That holds for engine against engine, not for you and your opponent at 1200.
Why can a +2 position still lose?
Because the evaluation assumes both sides play the best moves from here on, and humans don’t. A +2 position that needs five precise moves in a row is harder to win than a +1 position where every natural move works. The less time you have on the clock, the more that matters.
The number also changes as the engine thinks. An evaluation at depth 10 can change at depth 25 when the engine finds something it had missed, so in a sharp position give it a little longer before you believe it.
Why does the evaluation jump after one move?
Because that move gave something away. A jump from +0.4 to -2.5 after your move usually means you lost a piece or allowed a tactic. Game reviews label moves by that swing: a large drop gets called a mistake or a blunder, a small one an inaccuracy.
How do you see the evaluation of your own position?
Paste the FEN or the PGN into the free analysis board. Stockfish runs in your browser and shows the evaluation as a number and a bar, with its three best lines underneath, each with its own score. If the three numbers are close, several moves are fine. If the first one is far ahead of the others, the position had one good answer.
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