rating title

This program lets you estimate how your rating has changed after playing in a Chess tournament. Enter the ratings of all of your opponents (post-tournament if possible) in any of the twelve boxes below followed by your total score. Click the “Performance” button to see your estimated performance rating. Entering your current rating is optional, but required if you wish to see your estimated new rating.

Enter opponents rating ( up to 12 players )

Total Score      



Current Rating      
# of prior Games        



Chess Performance and Rating Calculator / by George C. John

This software is based on information contained in approximating formulas for the USCF Rating System.  See The USCF Rating System for more details.

You do not need to enter individual win, loss, draw results, only the total score (win=1.0, draw=0.5, and loss=0.0).  Click the “New Rating” button to see your new estimated rating.  Click on “Show K” to see the “K” value (see below for details) used in the calculation.  Click on “Show Bonus” to see how much of your rating change was due to the bonus calculation.

In the case of a perfect or zero score the performance rating is estimated as either 400 points higher or lower, respectively, than the rating of highest or lowest rated opponent.

The “K” factor represents an estimate of player rating volatility. The higher the value the more uncertain the prior rating is assumed to be, and therefore how rapidly a player’s rating may change. Its value is determined from number of prior games, number of games played in the current event, and prior rating.

For unrated players with no prior games, set “# of Prior Games” to zero (“Current Rating” will be ignored). When all games are either lost or won, Age is used to estimate a prior rating. If no value is entered for Age, a prior rating of 750 is assumed.

Note: A current limitation is the calculation may not be correct when all prior games have either been all wins or losses.

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