It's a complex calculation ... http://www.chess.com/article/view/chess-ratings---how-they-work
The number of points by which your rating will change is different for you and for your opponent. It also changes during the game, as your - or your opponent's rating changes. The only useful information you can find out is: how much your rating will change for a win, a loss and a draw at THIS POINT in THIS GAME. Use show rating adjustment, under the Details tab, for something like this:
Rated - Win: +16 Loss: -9 Draw: +4
can anyone give me a quick note on the ammount of points you win or lose when a game has ended and how it works, thanks