- 14 Oct '04 21:52

From FAQ...*Originally posted by schlodowec***How does RHP calculates the rating? Does anybody know?**

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. - 15 Oct '04 01:28 / 4 editsThanks, Ragnorak.

But it is a curious calculation. When the difference between the ratings is strong you do not have the rating decreased if you loose!

Let us see this example:

My rating is 400.

My opponent rating is 1200.

So, win spectancy would be 0.009901 and K is 32.

My new ratings then would be:

432 if I win (higher, ok)

416 if I draw (not bad...)

400 if I loose!!!

If my rating is 1200 and my opponent's rating is 400, my rating would remain the same if I win, but it'd be decreased in 16 points if I draw or 32 points if I loose the game.

Lesson to learn: never loose!!! :=)

Schlodowec

PS: BTW, I gave you 1 recomendation. Thanks for your time! - 15 Oct '04 09:21

Check out this thread for another way of looking at it...*Originally posted by schlodowec***But it is a curious calculation. When the difference between the ratings is strong you do not have the rating decreased if you loose!**

http://www.redhotpawn.com/board/showthread.php?threadid=13943

This isn't official, but there are enough smart people here to figure out if its close or not.

D