In chess, the chess pieces are often assigned certain point values that help determine how valuable a piece is strategically. These values are useful to players, and are also used in computer chess to help the computer figure out what moves to make. Calculations of the value of pieces provide a only rough idea of the state of play. The exact value of the piece will depend on the game situation.
The following is the most common assignment of point values.
The king is impossible to value since its loss causes the loss of the game. In some computer chess programs, the king is assigned roughly 200 points, a value appr. twice as high as the sum of all other pieces. This ensures that the computer will value checkmate over all exchanges or sacrifices.
Computer programs will typically make further adjustments to this score according to various positional factors. For example, a third of a point may be subtracted for doubled pawns, isolated pawns and backward pawns, fractions of points may be added for possession of open files, and so on. For most humans, such positional evaluation is done without reference to a numerical score.
In his book New Ideas in Chess, grandmaster Larry Evans gives the values pawn=1, knight=3.5, bishop=3.75, rook=5, and queen=10. However, the traditional valuations above seem to be more accurate. A bishop is usually worth slightly more than a knight, but not always. Bobby Fisher gave the value of the bishop as 3.25 (with the other pieces having the traditional value).
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