A centipawn is one hundredth of a pawn, and it is the unit chess engines use to report an evaluation. A score of 100 centipawns equals one pawn, which is why engines display 1.00 rather than 100. The unit allows the engine to express small differences that matter positionally but are not worth a whole pawn.
Centipawn is the currency chess engines use. It exists because pawns are too coarse a unit: two positions can both be up half a pawn, or one can be clearly better without ever winning material. The centipawn gives the engine room to express that.
The arithmetic
| Centipawns | Displayed as | Meaning |
|---|---|---|
| 0 | 0.00 | Level |
| 50 | +0.50 | Half a pawn |
| 100 | +1.00 | One pawn |
| 350 | +3.50 | Roughly the value of a piece |
| 900 | +9.00 | A queen, near enough |
Material values are the anchor. A pawn is a hundred centipawns, a knight or bishop about three hundred, a rook about five hundred, a queen about nine hundred. Everything else the engine adds is in effect saying: this positional feature is worth this fraction of a pawn.
Centipawn loss
Centipawn loss is the difference between the score after the best move and the score after the move you actually played, measured from your side's point of view. If the best move held the score at +0.20 and your move left it at -0.80, that move cost about a pawn, so a centipawn loss of one hundred.
This is the number move classifications are usually built on. A move that loses almost nothing is excellent, and a move that throws away several pawns is a blunder, with a band of inaccuracies and mistakes between them.
Where centipawns mislead
- Outside roughly plus or minus ten pawns the number stops being meaningful. A score of plus fifteen and plus twenty-five are both simply winning.
- Mate is not expressible this way, which is why forced mates get their own notation rather than a very large score.
- Tiny differences are noise. Twenty centipawns can be the difference between two engine versions rather than two moves.
- In dead-drawn endgames the score can wobble for reasons that have nothing to do with progress, and a tablebase would tell a different and more definitive story.
Reading scores sensibly
- Treat anything within about a tenth of a pawn as level.
- Focus on changes of a pawn or more, which is where real mistakes show up.
- Prefer the shape of the graph across a game to any single number in it.
- Remember that a score is relative to the depth and settings that produced it, so two analyses are only comparable when those match.