Rating calculation for an Unrated Player in Swiss Tournaments

“I have scored many points against rated players in several tournaments, but my rating is not published.” Why?

Rating calculation for an Unrated Player in Swiss Tournaments
R. Anantharam IA, Chairman, Arbiters’ Commission, AICF

An unrated players’ first ambition is to get international rating. To get rating, a player has to participate in FIDE rated tournaments, FIDE standing for “Federation Internationale des Echecs”, the World Chess Federation. Players may also be interested in knowing the criteria and procedure to get a rating. A brief account of the same is furnished below. For more details, a player has to refer http://www.fide.com/fide/handbook.html?id=172&view=article.

There are several types of tournaments in Chess – Swiss individual, Swiss team, Round Robin, Scheveningen etc. In Swiss tournaments, number of participants will be large (generally in hundreds in India) and number of rounds is limited (generally nine to eleven). In round robin tournament, a participant will play against all the remaining participants. Players of one team have to play only against players of another team in all rounds of a Scheveningen tournament. Most of the tournaments played in India are of Swiss type.

For an unrated player’s rating performance to begin, he must score at least half a point against rated players in a tournament. He will get a rating, after meeting five rated players (in one or more tournaments), provided his new rating is 1000 or above.

The condition of a minimum of 5 games need not be met in one tournament: Results from other events, played within rating period of not more than 26 months, are pooled to obtain the initial rating.

The rating is calculated using all his results and the rating data available, as if they were played in one tournament, but not published, until he has played at least 5 games against rated players. Suppose he meets 5 or more players within 2 months, his rating will be published in the following month rating list, provided the calculated rating is at least 1000.

If he scores 50%, then Ru = Ra (Ru is the new rating and Ra is the average rating).
If he scores more than 50%, then Ru = Ra + 20 for each half point scored over 50%.
If he scores less than 50%, in a Swiss or team tournament: then Ru = Rc + dp (rating differences)

Example: An unrated player has played 4 games in a tournament against rated players with average rating of 1800, then in another tournament 4 games against rated players with the average rating of 1650, and then in a third tournament 2 games against rated players with average rating of 1500. Let us assume that all these tournaments are in one rating period. The average rating of all opponents is (4 x 1800 + 4 x 1650 + 2 x 1500) ÷ 10 = 16800 ÷ 10 = 1680

Case 1: Assume the player has scored 2 out of 4 in first tournament 2.5 out of 4 in second and 1.5/2 in third tournament. The player’s initial rating is calculated as if he had played 10 games with a score of 2 + 2.5 + 1.5 = 6.0/10.

The result is 6.0 out of 10, it is two half (½) points more than 50 percent (5 + ½ + ½). For every half point, add 20 to the average rating. The new player’s first published rating is 1680 + (2 x 20) = 1720

Case 2: Assume the player has scored 3.0/4, 0/4 and 2.0/2 in the three tournaments. His total score is 5/10. This is 50% score and his new rating will be the average itself, i.e.1680.

Case 3: Assume the player has scored 1.5/4, 1.5/4 and 0/2 in the three tournaments. His total score is 1.5 + 1.5 + 0 = 3.0, which is less than 50%. His percentage is 3.0/10 = 0.30. The dp for 0.30 from the tables is -149. His new rating will be 1680 – 149 = 1531.

FIDE publishes the rating list every month. It also publishes rating list for Rapid and Blitz tournaments separately.

Inactivity :- A player is considered to commence inactivity if he does not play any rated games in one year period. A player regains his activity if he plays at least one rated game in a period and he is then listed on the next list.
For rating changes of a rated player, a factor called K is used.
K = 40 until he plays 30 rated games OR
K = 40 until 18th birthday of the player, as long as his rating remains under 2300.
K = 20 until he reaches 2400
K =10 after he reaches 2400
Dp table The table of conversion from fractional score, p, into rating differences, dp

p dp p dp p dp p dp p dp p dp
1.0 800 .83 273 .66 117 .49 -7 .32 -133 .15 -296
.99 677 .82 262 .65 110 .48 -14 .31 -141 .14 -309
.98 589 .81 251 .64 102 .47 -21 .30 -149 .13 -322
.97 538 .80 240 .63 95 .46 -29 .29 -158 .12 -336
.96 501 .79 230 .62 87 .45 -36 .28 -166 .11 -351
.95 470 .78 220 .61 80 .44 -43 .27 -175 .10 -366
.94 444 .77 211 .60 72 .43 -50 .26 -184 .09 -383
.93 422 .76 202 .59 65 .42 -57 .25 -193 .08 -401
.92 401 .75 193 .58 57 .41 -65 .24 -202 .07 -422
.91 383 .74 184 .57 50 .40 -72 .23 -211 .06 -444
.90 366 .73 175 .56 43 .39 -80 .22 -220 .05 -470
.89 351 .72 166 .55 36 .38 -87 .21 -230 .04 -501
.88 336 .71 158 .54 29 .37 -95 .20 -240 .03 -538
.87 322 .70 149 .53 21 .36 -102 .19 -251 .02 -589
.86 309 .69 141 .52 14 .35 -110 .18 -262 .01 -677
.85 296 .68 133 .51 7 .34 -117 .17 -273 .00 -800

A Lot of mails have been received by AICF recently, stating that – a player has scored many points against rated players from several rating tournaments, but his or her rating has not been published by FIDE. The reason is that, after calculating their rating in the above said manner, the resulting rating must at least be 1000. If it is less than 1000, the rating will not be published.

– If a player has scored 0.5 points from 5 games (0.10 percent from number of games), (When p is .10 then dp is -366 ) See Table above .

the Average Rating should at least be 1366 to get a rating of 1000.

– If a player has scored 1.0 point from 5 games (0.20 percent from number of games), the average rating should at least be 1240 to get a rating of 1000.

– If a player has scored 1.5 points from 5 games (0.30 percent from number of games), the average rating should at least be 1149 to get a rating of 1000.
Naturally, the rating obtained will be higher, if a player meets stronger opponents. And if a player has met players of rating around 1100 or less, it is difficult to get a good rating.

For further queries regarding rating, feel free to write to arbiter_commission_aicf@googlegroups.com