Chess piece relative value

In chess, the chess piece relative value system conventionally assigns a point value to each piece when assessing its relative strength in potential exchanges. These values help determine how valuable a piece is strategically. They play no formal role in the game but are useful to players and are also used in computer chess to help the computer evaluate positions.

Calculations of the value of pieces provide only a rough idea of the state of play. The exact piece values will depend on the game situation, and can differ considerably from those given here. In some positions, a well-placed piece might be much more valuable than indicated by heuristics, while a badly placed piece may be completely trapped and, thus, almost worthless.

Valuations almost always assign the value 1 point to pawns (typically as the average value of a pawn in the starting position). Computer programs often represent the values of pieces and positions in terms of 'centipawns' (cp), where 100 cp = 1 pawn, which allows strategic features of the position, worth less than a single pawn, to be evaluated without requiring fractions.

Edward Lasker said "It is difficult to compare the relative value of different pieces, as so much depends on the peculiarities of the position...". Nevertheless, he said that bishops and knights (minor pieces) were equal, rooks are worth a minor piece plus one or two pawns, and a queen is worth three minor pieces or two rooks (Lasker 1915:11).

The following table is the most common assignment of point values (Capablanca & de Firmian 2006:24–25), (Seirawan & Silman 1990:40), (Soltis 2004:6), (Silman 1998:340), (Polgar & Truong 2005:11).

These values are very reliable in endgames with a limited number of pieces. The oldest derivation of the standard values is due to the Modenese School (Ercole del Rio, Giambattista Lolli, and Domenico Lorenzo Ponziani) in the 18th century (Lolli 1763:255) and is partially based on the earlier work of Pietro Carrera (Carrera 1617:115–21). The value of the king is undefined as it cannot be captured, let alone traded, during the course of the game. Some computer chess programs give the king an arbitrary large value (such as 200 points or 1,000,000,000 points, for example Zillions of Games gives 106332 points for king vs. 14332 points for queen in center) to indicate that the inevitable loss of the king due to checkmate trumps all other considerations (Levy & Newborn 1991:45), as that is the easiest way to create a computer chess program due to technology limits. In the endgame, where there is usually little danger of checkmate, the fighting value of the king is about four points (Lasker 1934:73). In the endgame, a king is more powerful than a minor piece but less powerful than a rook. Julian Hodgson also puts its value at four points (Aagaard 2004:12). The king is good at attacking and defending nearby pieces and pawns. It is better at defending such pieces than the knight is, and it is better at attacking them than the bishop is (Ward 1996:13).

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