Chess Elo Rating Difference Calculator

This section will calculate the difference in Elo rating between two players from match results or winning percentage. (Margin of error uses 95% confidence.)

Wins Losses Draws
Winning percentage

Elo difference :
error margin :

Elo Rating Change Calculator

This section will calculate the change in a player's Elo rating after playing a single game against another player. The value K is the maximum change in rating.

Player Elo   : K :
Against Elo :

Win Draw Loss

Expected Percentage :

Wikipedia Elo
see for details on the formula used for the calculations. (You can also right click on this page and View Page Source to see my Javascript code.)

Slow Chess Blitz
my freeware chess program.

GuiNN Checkers
my freeware neural network checkers program.