Engine evaluation

An engine evaluation is an estimate produced by a chess engine, a program that compares many possible continuations. It is often displayed as a number such as +0.40 or -1.20. Many interfaces use positive values for a White advantage and negative values for a Black advantage, while others show the score from the player's or side-to-move perspective. The interface convention must therefore be checked.

Numeric scores are commonly expressed in centipawns, units equal to one hundredth of a pawn on the engine's scale. This does not mean that +1.00 always represents one extra pawn on the board. The score also reflects king safety, activity, structure, and future possibilities. Forced mates, sequences that inevitably leave the king with no legal defense, are normally displayed separately because mate is not a gradual advantage.

The displayed result combines an estimate of reached positions with a search through move sequences. The principal variation is the best line the engine found within the available time, the reached depth, a measure of how far the analysis advanced through continuations, and the chosen settings. More analysis, a different engine version, or changed options may alter both the number and the line.

How to read it

• A value near 0.00 usually means approximate balance, not necessarily an easy game or a guaranteed draw.
• A large advantage means the engine sees a favorable path, but the number alone does not explain how to play it.
• A sharp change after one move helps locate a critical moment; the next task is to identify the reason.
• Scores from different engines or settings are not always directly comparable.

A static evaluation is an immediate estimate of a position before its continuations are searched deeply. The value shown to a user normally includes search as well, so it may uncover tactical resources that a static impression misses.