How Do I Know When to Trade Pieces?

When to trade pieces in an even exchange: There are a number of reasons why to or not to make these trades. It really comes down to the exact position of the board, and what positional factors are in play on the board. Both for you and your opponent.

First (and the most obvious) is if the exchange is forced, or is the only way to not lose material (or for that matter lose the least amount of material when you are going to lose material anyways).

Second is you have material advantage. The logic behind this is that when up material your material advantage is greater when there is less pieces on the board. So for example if you are up a full knight in material, and the only piece off the board is that knight you won, then your material advantage is less of an advantage than if there are only pawns, kings, and your knight left on the board. So every even trade of material you make when you have material advantage increases that advantage. This even applies to just being up a pawn also because if you have an extra pawn in the endgame then you have the chances to queen that pawn and win the game.

Third is when your opponent has a space advantage. This is because when your opponent has less pieces left on the board then they can not use that space advantage as well, and also gives you more breathing room in that case. Conversely if your have the space advantage then you don't want to make even trades unless you getting something else in return for the exchange.

Fourth is when you are defending. If your opponent is attacking you, then one of the ways to defend against the attack is to trade off pieces that your opponent is attacking with. If their pieces are off the board then they can't attack with them. Making the attack not as dangerous typically. Conversely if you are the one doing the attacking then you don't want to make even trades with out getting another advantage in the position, or if helps make the become more powerful and unstoppable.

Fifth is the bishop vs knight battle. This comes down to what the position is or is going to be. Bishops do better than knights in open spaces, and knights do better than bishops in closed positions. So if the position is open then if you can trade one of your knights for your opponents bishop then it probably a good thing to do. If the position is closed with pawns locked in the center then if you can trade a bishop (which will have a hard time moving, and controlling squares) for a knight which will be able to jump over those pawns and control squares. Also when it comes to bishops vs knights having the bishop pair can be beneficial because one bishop can only control one color of squares, and a knight can control squares of both colors. So when it comes to coordination knights can coordinate to control different squares of either colors, and bishops can't do that. Having the bishop pair can be vary valuable late in the game. So denying that in a game can be a good for you to do, and be valuable to have that advantage.

Sixth is prevent falling behind in development in the opening. It can be good to make an even trade to prevent falling behind in development.

Seventh is to create some other positional weakness. An example of this would be to create doubled pawns which can be weak, and be more problematic late in the game especially. Conversely making an even trade that results in a positional weakness is generally better to be avoided.

Hope this helps.

Read the book "My System". There's a section there dedicated for exchanging pieces. Previous post already gave good pointers. Another reason is exchanging to "gain tempo". Basically if you don't have to and there's no gain from it, don't exchange. The question is what kind of gain you get. Is it time, is it material, or outright checkmate?