Each player begins with a rating of 1500. Ratings are increased or decreased when a player wins or loses rated matches. The ratings change for each match is based on the length of the match and the ratings difference between the players. The longer the match, the more ratings points are risked.

Since the higher-rated player is more likely to win a match, especially as the match length increases, a lower-rated player gets favorable odds when playing a higher-rated player. For example, suppose a player rated 1550 challenges a player rated 1850 to a 7-point match. The player rated 1550 stands to gain 7.7 rating points if he wins, and lose only 2.9 rating points if the higher-rated player wins. Conversely, The player rated 1850 stands to gain only 2.9 rating points if she wins, but lose 7.7 rating points if the lower-rated player wins.

These numbers reflect the match winning chances (MWC) for each player, based on the difference in rating and length of the match. (In the example, the lower-rated player has approximately 27% MWC, and the higher-rated player 73% MWC). The win/lose numbers are shown in the invitation dialogue.

There is an initial adjustment period of 500 games (called "the ramp"). During this period, your rating will change more rapidly, in order to more quickly adjust to an appropriate level. Using the same example as above, if the lower-rated player had only 5 experience points, he would stand to gain 30.8 rating points if he wins, and lose 11.5 rating points if he loses. (The risks for the higher-rated player remain the same, assuming more than 500 experience points.) As your experience approaches 500 games, the rate of change decreases to the standard rate.

For this reason, experienced players will offer a simple resignation in a hopeless position, when the current cube value is sufficient to give their opponent the match. Their opponent should accept it, and record the win, even if a gammon is possible. While they are within their rights to play the game out, there is no ratings benefit to wasting the time. They should accept their match victory graciously, and move on to the next match.

In order to start at a higher rating, a nickname must be a newly created on GamesGrid (no experience points) with a minimum membership commitment of 6 months. Transfer of membership from another GamesGrid nickname for this purpose is not permitted.

We currently recognize the following equivalencies for players from other backgammon sites:

The equivalencies may change from time to time, and we reserve the right to modify the formulae at any time in order to maintain the fairness of the rating system.

last modified: 2005-04-27