A chess rating system is a system used
in chess to calculate an estimate of the strength of the player, based on his or
her performance versus other players. They are used by organizations such as
FIDE, the US Chess Federation, International Correspondence Chess
Federation, and the English Chess Federation. Most of the systems are used
to recalculate ratings after a tournament or match but some are used to
recalculate ratings after individual games. In almost all systems a higher
number indicates a stronger player. In general, players’ ratings go up if they
perform better than expected and down if they perform worse than expected. The
magnitude of the change depends on the rating of their opponents. The Elo
rating system is currently the most widely used.
The first modern rating system was used by the Correspondence Chess League of
America in 1939. Soviet player Andrey Khachatoruv proposed a similar system in
1946. The first one that made an impact on international chess was the Ingo
system in 1948. The USCF adopted the Harkness system in 1950. Shortly after,
the British Chess Federation started using a system devised by Richard W. B.
Clarke. The USCF switched to the Elo rating system in 1960, which was adopted
by FIDE in 1970. Ingo system
The Ingo system was designed by Anton Hoesslinger and published in 1948. It
was used by the West German Chess Federation from 1948 until 1992, when it
was replaced by an Elo-based system, Deutsche Wertungszahl. It influenced
some other rating systems. This is a simple system where players’ new ratings
are the average rating of their competition minus one point for each
percentage point above 50 obtained in the tournament. Unlike most other
systems, lower numbers indicate better performance.
Harkness system The Harkness System was invented by
Kenneth Harkness, who published it in 1956. It was used by the USCF from 1950
to 1960 and by some other organizations. When players compete in a tournament,
the average rating of their competition is calculated. If a player scores 50%,
they receive the average competition rating as their performance rating. If
they score more than 50%, their new rating is the competition average plus
10 points for each percentage point above 50. If they score less than 50%,
their new rating is the competition average minus 10 points for each
percentage point below 50.=Example=
A player with a rating of 1600 plays in an eleven-round tournament and scores
2½–8½ against competition with an average rating of 1850. This is 27.3%
below 50%, so their new rating is 1850 –=1577.
English Chess Federation system The English Chess Federation Grading
System was devised by Richard W. B. Clarke and first published in 1958.
Points are scored for every game played in a registered competition. A player’s
grade is calculated by taking the opponent’s grade and adding 50 points
for a win, subtracting 50 points for a loss, and taking the opponent’s grade as
it stands for a draw. For grading purposes it is assumed that the
opponent’s grade is never more than 40 points above or below one’s own. The ECF
grades approximately 200,000 games a year. The grading season runs from 1
June to 31 May. An ECF grade can be approximated to an Elo rating by
multiplying by 7.5 and adding 700. An ECF grade of 100 is approximately 1450
Elo, while 200 ECF equals 2200 Elo. Elo rating system
The Elo system was invented by Arpad Elo and is the most common system. It is
used by FIDE and other organizations. FIDE classifies tournaments into
categories according to the average rating of the players. Each category is
25 rating points wide. Category 1 is for an average rating of 2251 to 2275,
category 2 is 2276 to 2300, etc. For women’s tournaments, the categories are
200 rating points lower, so a Category 1 is an average rating of 2051 to 2075,
etc. US Chess uses a modification of the Elo
system, where the K factor varies and there are bonus points for superior
performance in a tournament. US Chess classifies players according to their
rating. US Chess ratings are generally 50 to 100 points higher than the FIDE
Elo gives an example of calculating the rating of Lajos Portisch, a 2635-rated
player, in an actual tournament of 16 players, and scored 10½ points. First
the difference in rating is calculated for each other player, subtracting the
other player’s rating from Portisch’s rating. Then the expected score against
each player is determined from a table, based on this rating difference. For
instance, one opponent was Vlastimil Hort, who was rated at 2600. The rating
difference of 35 gave Portish an expected score of 0.55. The expected
score is summed for each opponent, giving Portisch a total expected score
of 9.66. Then the formula is: new rating=old rating + K×(W-We),
where K=10, W=actual score, and We=expected score.
Portisch’s new rating is 2635+10×(10.5–9.66)=2643.4.
=Linear approximation=Elo devised a linear approximation to
his full system. With that method, a player’s new rating is
where Rnew and Rold are the player’s new and old rating respectively, Di is the
opponent’s rating minus the player’s rating, W is the number of wins, L is
the number of losses, C=200 and K=32.
The example of Portisch with K=10, with the sum of the rating differences
being 1620 is: US Chess used a modification of this
system to calculate ratings after individual games of correspondence
chess, with a K=32 and C=200. Glicko rating system
The Glicko system was invented by Mark E. Glickman as an improvement of the Elo
system. The Glicko-2 system is a refinement and is used by the Australian
Chess Federation and some online playing sites.
USA ICCF system The ICCF U.S.A. used its own system in
the 1970s. Now it uses the Elo system. Deutsche Wertungszahl
The Deutsche Wertungszahl system replaced the Ingo system in Germany.
Chessmetrics The Chessmetrics system was invented by
Jeff Sonas. It is based on computer analysis of a large database of games
and is intended to be more accurate than the Elo system.
Chronology 1933 – The Correspondence Chess League
of America is the first national organization to use a numerical rating
system. It chooses the Short system which clubs on the west coast of the US
had used. In 1934 the CCLA switched to the Walt James Percentage System but in
1940 returned to a point system designed by Kenneth Williams.
1942 – Chess Review uses the Harkness system, an improvement of the Williams
system. 1944 – The CCLA changes to an improved
version of the Williams system devised by William Wilcock. A slight change to
the system was made in 1949. 1946 – The USSR Chess Federation uses a
non-numerical system to classify players.
1948 – The Ingo system is published and used by the West German Chess
Federation. 1949 – The Harkness system is submitted
to the USCF. The British Chess Federation adopts it later and uses it
at least as late as 1967. 1950 – The USCF starts using the
Harkness system and publishes its first rating list in the November issue of
Chess Life. Reuben Fine is first with a rating of 2817 and Sammy Reshevsky is
second with 2770. 1959 – The USCF names Arpad Elo the head
of a committee to examine all rating systems and make recommendations.
1961 – Elo develops his system and it is used by the USCF. It is published in the
June 1961 issue of Chess Life. 1970 – FIDE starts using the Elo system.
Bobby Fischer is at the top of the list. 1978 – Elo’s book on his rating system
is published. 1993 – Deutsche Wertungszahl replaces
the Ingo system in Germany. 2001 – the Glicko system is published.
2005 – Chessmetrics is published by Jeff Sonas.
See also Chess engine rating lists
Sports rating system List of FIDE chess world number ones
Elo, Arpad, The Rating of Chessplayers, Past and Present, Arco, ISBN
0-668-04721-6 Harkness, Kenneth, The Official Chess
Handbook, McKay Hooper, David; Whyld, Kenneth, The
Oxford Companion to Chess, Oxford University Press, ISBN 0-19-280049-3
Just, Tim; Burg, Daniel B., U.S. Chess Federation’s Official Rules of Chess,
McKay, ISBN 0-8129-3559-4 Lawrence, Al, “Ratings, Rules, and
Rockets: USCF’s 2nd decade: 1949–1958”, Chess Life 2009: 9
External links Chessbase article
Chessmetrics website approximate USCF ratings
Elo system and chess rating calculation in FIDE
Interactive world map of FIDE country rankings
Complete World Chess Rating List A two dimensional measure of chess