How to Estimate a Rating Change in your Head

 

The difference in ratings between two players is designed to reflect the probability of winning in a match between the two players.  Because higher rated players have a greater probability of winning against lower players, their reward in rating points is not as great as when the ratings were the same.  By the same token, the penalty in rating points for the lower rated losing player is not as great.   Conversely, when the lower rated player wins, he is rewarded more than if the ratings were the same and the higher rated player is penalized more.

For any rated game, the maximum number of points at stake is 32.

Here is how you can figure out how many points you won or lost without having to look it up on a chart.

Keep the number 32 in mind.
When you play someone at the same rating as you, regardless of what that rating is, you are each playing for 16 points (half of 32). The winner gets 16 points and the looser looses 16 points.
Lower rated player wins
For every 100 point difference in rating, the lower rated player gets rewarded with 4 more points than if he had the same rating as his opponent.  For example,  1400 player beats 1500 player, the 1400 player gets 20 points.  1400 player beats a 1600 player, the 1400 player gets 24 points.
  
Higher rated player wins
For every 100 point difference in rating, the higher rated player gets 4 less points than if he had the same rating as his opponent.  For example,   1500 player beats a 1400 player, the 1500 player gets 12 points.  1500 player beats a 1300 player, the 1500 player gets 8 points. 
Whatever the higher rated player wins, the lower rated player loses.
  
Another shortcut
If you calculate out just one of the results, either lower or higher player winning, to get the other result subtract the number from 32.  For example, a 1500 beats a 1400 player, the 1500 gets 12 points.  If he loses, he loses 32-12 or 20.
Draws
Take however many points you stood to win and subtract 16 from it.   If you have the same rating the result is 0 since you stood to win 16.  If you are lower rated by 100 points, you get 20 - 16 = 4.  If you are higher rated by 16 you get 12 - 16 = - 4.