How Chess Move Ratings Work

Chess move ratings are usually determined by a chess engine, which is a powerful computer program that analyzes the board and evaluates positions. Chess engines range from electronic chess computers to online play sites like Chess.com or LiChess.

The basic idea

After each move in a game, the engine looks at the position and calculates what it believes is the strongest move available. It then compares the move that was actually played to that best option.

How engines score positions

Chess engines score positions using a numerical evaluation, typically measured in pawns. For example, +1.00 means White is roughly one pawn better, while -1.00 means Black has about a one-pawn advantage.

How a move gets its rating

If the move played keeps the evaluation close to the best move, it will receive a high rating. If the move causes the position to become significantly worse compared to the engine’s best line, it will be labeled accordingly.

Common move rating labels

• Best move – the engine’s top choice
• Excellent or Great – nearly as strong as the best move
• Good – solid, but not optimal
• Inaccuracy – slightly weak
• Mistake – gives up a noticeable advantage
• Blunder – loses major material or a winning position

These labels are simply a way to help players see where a move kept the position strong or where it caused the game to slip.

In short, move ratings come from comparing a played move to the best move a chess engine can find and measuring how much the position improves or worsens as a result.