Evaluation bar
The evaluation bar is a vertical or horizontal gauge beside the board that shows, with a bar of black and white, which side the engine thinks is better and by roughly how much.
Also called: eval bar
The evaluation bar is a quick visual summary of the engine’s score. The white portion grows when White is doing better and the dark portion grows when Black is. A bar split evenly means the position is roughly equal. Many analysis boards also print the number beside it, such as plus 1.2, and show a mate message when a forced checkmate exists.
The bar is useful for finding the moment a game turned. Step through the moves and watch where it jumps. Those jumps point to blunders, missed tactics and brilliant resources, so you can spend your review time where it matters most.
Be careful with it during study. If you leave the bar visible while solving a puzzle or analyzing a position, you see the verdict before you have thought, and the exercise loses its value. Hide the bar until you have decided on your own move and your own plan. The bar also reflects the engine's own best play, and it can look dramatic in positions where a human would find it hard to make use of the advantage, so read it as guidance and not a final judgment.
Compare it with Centipawn. A centipawn is one hundredth of a pawn, the small unit engines use to report evaluations, so a score of 150 centipawns means the engine thinks one side is about one and a half pawns better.
A neighboring idea is Blunder check. A blunder check is a quick test, made by a person before moving or by software afterward, that looks for a move which hangs material, allows a tactic or loses the game outright.
Computer terms such as "Evaluation bar" are most useful next to a coach who reads your games with you, which is how a first lesson with George Li works.
Related terms
An evaluation is a numerical judgment of who stands better in a position, usually given in pawns from White’s point of view, where positive favors White and negative favors Black.
A centipawn is one hundredth of a pawn, the small unit engines use to report evaluations, so a score of 150 centipawns means the engine thinks one side is about one and a half pawns better.
A chess engine is a computer program that searches positions and evaluates moves, usually playing and analyzing far stronger than any human, and it is used for analysis, preparation and play against a machine.
Engine analysis is the use of a chess program to search a position and report which moves are strongest, along with a numeric evaluation and the lines it expects both sides to follow.
Post-game analysis is the discussion or private review held right after a game, in which both players or one player alone retrace the moves and identify the turning points, missed ideas and lessons.
A blunder check is a quick test, made by a person before moving or by software afterward, that looks for a move which hangs material, allows a tactic or loses the game outright.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
How much does chess coaching cost?
Published rates for private, group and subscription chess coaching, with the source and the date of each.
A game review, a read on your level and a written study plan from George Li.
Want to spot this in your own games?
A first lesson starts with your games: George reviews them and builds a study plan around what he finds.