The strength of a chess piece is mainly determined by how many different squares it can control at a given time. Therefore the strength of a piece is partly determined by the location it is on the board. Most pieces are strongest near the center. The Queen is the most powerful piece. From the center of the board she can control 27 squares.

	The Rook is the next most powerful piece. From the center of the board a Rook can control 14 squares. An odd characteristic of the Rook is that it is the only piece that doesn't lose power when it is at the edge of the board. From the edge of the board, or even in a corner, the Rook can still control 14 squares.

A Bishop in the center of the board can control 13 squares. Although this is just one less than the Rook, it has an additional weakness in that it can only control squares of one color. A light-squared Bishop must always stay on light squares and a dark-squared Bishop must always stay on the dark squares.

A Knight in the center of the board can control 8 squares. This is a short-ranged piece because it cannot move across the board in a single bound as the previously mentioned pieces can. When you compare the Knight to the Bishop at first glance it seems like the Bishop is much more powerful, however the Knight is the only piece that can jump over other pieces and is not limited to only the light or dark squares as the Bishop is. A Knight is roughly the same strength as a Bishop.

The weakest piece on the board is the Pawn. It can only move one square at a time straight ahead with an option of moving two squares on its first move. It is the only piece that doesn't capture the same way as it moves. It attacks the squares at the immediate front left and right diagonals so at most it can only attack two squares at any given time. Another unique feature of the Pawn is that once it gets to the opposite side of the board it can be promoted to another piece. Due to this promotion threat Pawns tend to gain strength as pieces leave the battlefield and their path to promotion becomes easier.

All good chess players should memorize these values. Knowing the value of the pieces will help you analyze positions and will help you know which exchanges are good for you and which are bad. On the other hand, these values should not be taken as the absolute gospel. Chess is a complicated game full of exceptions. For example, a single passed Pawn can be worth a Rook if that Rook must sacrifice itself to stop the Pawn from Queening. Two Rooks are usually stronger than a Queen but in many situations the Queen prevails. Two Bishops are valued the same as two Knights but the Bishop pair is almost always stronger. As you become a more experienced chess player you will learn more situations when pieces gain or lose strength.