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Understanding Engine Evaluations: Centipawns, Mates & The Bar

Walk into any modern chess broadcast, and you will see a black-and-white bar fluctuating on the side of the screen. You'll see numbers like +0.75 or -M4. For beginners, this can be confusing. For advanced players, misinterpreting these numbers can lead to bad analysis.

This guide breaks down exactly how engines "score" a chess position and how to translate those computer numbers into human concepts.

The Centipawn System

Engines do not think in "good" or "bad." They think in math. The standard unit of measurement is the Centipawn (cp). 100 centipawns roughly equal the value of one pawn.

Note: Positive numbers (+) favor White. Negative numbers (-) favor Black.

The Scale of Advantage

0.00 to +0.30 (Equal): The position is balanced. A "drawish" game.
+0.30 to +0.90 (Slight Advantage): White has pressure. This might be a space advantage, a safer king, or the bishop pair. In human play, this is comfortable, but not winning.
+1.00 to +1.50 (Clear Advantage): White is essentially "up a pawn" in value. At the Grandmaster level, this is often decisive.
+2.00 and above (Winning): Unless there is a fortress, the side with this advantage should win 95% of the time.

Special Engine Codes

Sometimes the numbers disappear and are replaced by symbols.

#M5 (or +M5): Mate in 5. White can force a checkmate in exactly 5 moves, no matter what Black plays. The evaluation is no longer about material; it is about ending the game.
-M3: Mate in 3 for Black. Black has the forced win.
0.00 (The Fortress): Sometimes, you might be down a Queen for a Rook (materially losing), but the engine says 0.00. This usually indicates a Fortress—a position where the opponent cannot break through despite their material advantage.

The "Horizon Effect" & Depth

Have you ever seen an evaluation jump from 0.00 to -5.00 in one move, even though the move looked normal? This is called the Horizon Effect.

Engines calculate to a certain "depth" (e.g., 20 moves deep). If a trap exists at move 25, the engine might not see it yet. Once the game progresses closer to that trap, the engine suddenly "sees" it over the horizon, and the evaluation crashes. This is why running an engine at low depth (on a phone) can sometimes be misleading compared to a cloud engine running at high depth.

Human vs. Computer Evaluation

Warning: A +0.8 advantage is meaningless if the position is impossibly sharp and requires 10 computer-perfect moves to survive. Always look at the nature of the position, not just the number. A messy 0.00 is often better for a human than a stable -0.30.