Every piece on the board has a definite numerical value and understanding these values is the key to winning. Every chess piece is given a relative point value, except for the king. In this value system pawns are worth one point, knights and bishops are worth three points each, a rook is worth five points, and finally a queen is worth nine points. Understanding the relative point values of these pieces will help you to determine if an exchange is worthwhile to you or not.
When you are considering giving up some of your pieces for some of your opponent's pieces you should think about the values of the pieces and not just how many each player possesses. The player whose pieces add up to a greater value will usually have the advantage. So a crucial step in making decisions is to add up the value of each player's pieces.
This simple mathematical process can help you make the decision of whether or not you want to make that trade with your opponent or not. These values have long been used and accepted by chess players the world over. There is little debate over whether or not the values are valid. Always assess this numerical value of pieces before you make that tempting trade with your opponent since you may end up on the mathematical losing end of the trade. If it takes you three pawns in order to capture a rook is it worth it? You can determine this by the numerical values. A pawn is worth one point and a knight is worth three points, so three pawns for a knight is a fair trade according to the values of the pieces. You can apply this formula to any trades that you are considering on the board.