- 11 Dec '04 15:24From the FAQ:

*How is my rating calculated?*

When you join, you are given a rating of 1200.

If you enter into a rated game, your rating will be recalculated on its completion so long as at least two moves have been made by each player.

Note: Until you have completed 20 games your rating may go down even when you win a game!

Until you complete 20 games, you will have a provisional rating. This rating is calculated as the average of all the games you have played. Each game is scored as being your opponent's rating (for a draw), your opponent's rating plus 400 (for a win), or your opponent's rating minus 400 (for a loss). If your opponent is also on a provisional rating, then the 400s above become 200s. If your opponent has played fewer than five games then their rating is treated as 1200 when calculating your rating.

Players are rated using the following formula:

New Rating = Old Rating + K * (Score - Win Expectancy)

K is a constant (32 for 0-2099, 24 for 2100-2399, 16 for 2400 and above)

Score is 1 for a win, 0.5 for a draw and 0 for a loss.

The Win Expectancy is calculated using the following formula :

Win Expectancy = 1 / (10^((OpponentRating-YourRating)/400)+1)

The Win Expectancy is used in the rating calculation but is interesting on its own. For example, the calculation below is for a rating difference of 200. This shows that if you have a rating 200 points higher than another player, you can expect to beat them, on average, three times for each four games played.

Win Expectancy = 1 / (10^(-200/400)+1) = 0.76

Note: ^ = "to the power of", e.g. 2^3=8.

If you have a non-provisional rating and you play a provisional-rated player, then you receive (or lose) only half the number of rating points you would normally. If the provisionally-rated player has played fewer than five games, then their rating is treated as 1200 when calculating your rating. - 11 Dec '04 17:58 / 1 editMight be easier to say...

Your provisional rating is calculated as an average of your opponents ratings ,+400 if you win and -400 if you lose to your opponents rating.

If you beat someone with a rating of 1100, then that would add 1500 into your average. If you lose to someone rated 1600 then that would add 1200 into our average. - 13 Dec '04 04:42

Um, I could have sworn that's what the part about provisional ratings says! Most of the FAQ is about general ratings, there's one main paragraph on provisionals and it says it pretty simply.*Originally posted by Saint Nick***Might be easier to say...**

Your provisional rating is calculated as an average of your opponents ratings ,+400 if you win and -400 if you lose to your opponents rating.

If you beat someone with a rating of 1100, then that would add 1500 into your average. If you lose to someone rated 1600 then that would add 1200 into our average. - 13 Dec '04 16:24

Yep, it's exactly what it says..*Originally posted by orfeo***Um, I could have sworn that's what the part about provisional ratings says! Most of the FAQ is about general ratings, there's one main paragraph on provisionals and it says it pretty simply.**

I was just trying to re-state it a little differently and give an example since it seems to cause alot of confusion for new poeple.

Sorry if it was redundant