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

equivalents.=Example=

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

Notes References

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

performance