Submission rejected on 21 June 2026 by ChrysGalley (talk). The subject does not meet Wikipedia's criteria for inclusion. Rejected by ChrysGalley 56 days ago. Last edited by 331dot 56 days ago. Ask for advice

Submission declined by ChrysGalley (talk). This draft appears to contain text generated by a large language model (such as ChatGPT). You cannot use LLMs to generate article content. LLM-generated pages with certain obvious signs of being machine generated may be deleted without notice. Instead, only summarize in your own words a range of independent, reliable, published sources that discuss the subject. See the advice page on large language models for more information. This draft does not include any sources or inline citations. Wikipedia's verifiability policy requires that all content be supported by reliable sources. You should also use inline citations (footnotes) to show which source supports which specific statement. The draft requires multiple published secondary sources that: provide significant coverage: discuss the subject in detail, not just brief mentions or routine announcements; are reliable: from reputable outlets with editorial oversight; are independent: not connected to the subject, such as press releases, the subject's own website, or sponsored content. Please add references that meet all three of these criteria. If none exist, the subject is not yet suitable for Wikipedia. You must place an inline citation directly after: quotations; any material whose verifiability is likely to be challenged or is contentious; any material about living people. Learn how to create inline citations in the: Source Editor: Introduction to referencing with Wiki Markup. VisualEditor: Introduction to referencing with VisualEditor. Declined by ChrysGalley.

Submission declined by ScalarFactor (talk). This draft appears to contain text generated by a large language model (such as ChatGPT). You cannot use LLMs to generate article content. LLM-generated pages with certain obvious signs of being machine generated may be deleted without notice. Instead, only summarize in your own words a range of independent, reliable, published sources that discuss the subject. See the advice page on large language models for more information. This draft does not include any sources or inline citations. Wikipedia's verifiability policy requires that all content be supported by reliable sources. You should also use inline citations (footnotes) to show which source supports which specific statement. The draft requires multiple published secondary sources that: provide significant coverage: discuss the subject in detail, not just brief mentions or routine announcements; are reliable: from reputable outlets with editorial oversight; are independent: not connected to the subject, such as press releases, the subject's own website, or sponsored content. Please add references that meet all three of these criteria. If none exist, the subject is not yet suitable for Wikipedia. You must place an inline citation directly after: quotations; any material whose verifiability is likely to be challenged or is contentious; any material about living people. Learn how to create inline citations in the: Source Editor: Introduction to referencing with Wiki Markup. VisualEditor: Introduction to referencing with VisualEditor. Declined by ScalarFactor.

• Comment: Let's block this for now. Just resubmitting without changes, and playing around with the header data to swap "decline" for "accept", is not the right way forward here. ChrysGalley (talk) 09:05, 21 June 2026 (UTC)

• Comment: Same problem as before. ChrysGalley (talk) 08:58, 21 June 2026 (UTC)

Template:Chess navigation

The Elo rating system is a method for calculating the relative skill levels of players in zero-sum games such as chess. It is named after its creator Arpad Elo, a Hungarian-American physics professor.

The system was developed as an improved chess rating system over the previously used Harkness system. It is also used as a rating system for competitive multiplayer video games, association football, American football, basketball, and various other sports.

Arpad Elo was a chess master and a unique figure in the United States Chess Federation (USCF) from its founding in 1939. The USCF used a numerical rating system devised by Kenneth Harkness, which allowed trackable numerical progress. While popular, the Harkness system was statistically flawed and easily manipulated.

On behalf of the USCF, Elo devised a new system based on statistical probability. The Elo system was adopted by the USCF in 1960 and by FIDE, the International Chess Federation, in 1970. Elo described his work in detail in his 1978 book, The Rating of Chessplayers, Past and Present.

The Elo system models game outcomes as a random variable following a probability distribution. The original system assumed a normal distribution, while FIDE and modern implementations generally use a logistic distribution.

When Player $A$ with rating $R_A$ plays Player $B$ with rating $R_B$, the formula for the expected score $E_A$ of Player $A$ is:

${\displaystyle E_{A}={\frac {1}{1+10^{(R_{B}-R_{A})/400}}}}$

Similarly, the expected score for Player $B$ is:

${\displaystyle E_{B}={\frac {1}{1+10^{(R_{A}-R_{B})/400}}}}$

When a player's actual tournament score exceeds their expected score, the rating increases. The core updating formula is:

${\displaystyle R'_{A}=R_{A}+K(S_{A}-E_{A})}$

Where:

• $R_A$ is the old rating.
• $R'_A$ is the new rating.
• $K$ is the development coefficient (K-factor).
• $S_A$ is the actual score (1 for a win, 0.5 for a draw, 0 for a loss).
• $E_A$ is the expected score.

The K-factor determines how aggressively a rating changes based on recent results. A high K-factor causes rapid changes, while a low K-factor ensures stability.

FIDE splits the K-factor into distinct tiers to balance volatility and experience:

• K = 40: For players new to the rating list until they have completed events with at least 30 games, or for all players until their 18th birthday as long as their rating remains under 2300.
• K = 20: For players with a rating always under 2400.
• K = 10: For players with a rating of at least 2400, once they have reached it. It remains 10 even if their rating drops below 2400.
• K = 20: For all rapid and blitz ratings.

FIDE awards lifetime titles based on performance and achieving specific Elo thresholds:

Despite its widespread adoption, the Elo rating system faces several mathematical and practical limitations.

Inflation occurs when the average rating of the active player pool increases over time. Deflation occurs when the average rating drops.

• Deflation causes: Master-level players retiring and taking points out of the system, or modern engines creating highly accurate defensive play.
• Inflation causes: Flooding the system with unearned starting points for new players.

FIDE historically used a rating floor (e.g., 1000 or 1400). Players dropping to this floor can artificially distort the calculations of opponents who defeat them, as their true strength might be lower than the floor indicates.

Because Elo is a relative system, a rating of 2200 in 1980 does not mathematically guarantee the exact same skill level as a 2200 rating in 2026. This makes cross-generational comparisons difficult.

Several modern rating models attempt to fix the flaws of the standard Elo system:

• Glicko rating system: Invented by Mark Glickman, it introduces "Rating Deviation" (RD) to measure the uncertainty of a player's rating based on inactivity.
• Universal Rating System (URS): Developed to combine classical, rapid, and blitz performances into a single, unified rating profile.
• Chess.com / Lichess Glicko-2: Major online platforms use variants of Glicko to handle the extreme volume and volatility of online pool data.

• Chess engine rating lists
• Comparison of top chess players throughout history
• Glicko rating system
• Performance rating (chess)

• Elo, Arpad (1978). The Rating of Chessplayers, Past and Present. Arco. ISBN 0-668-04721-6.
• Glickman, Mark (1995). "A Comprehensive Guide to Chess Ratings". American Chess Journal.

Category:Chess ratings Category:Evaluation Category:Zero-sum games