Noble's Pond Chess Club

ELO Calculator

The form below uses the ELO rating system to calculate chess ratings. Scroll down to learn about this often-used rating system.

Elo Rating Change Calculator

This section will calculate the change in a player's Elo rating after playing a single game against another player. The value K is the maximum change in rating.
Player Elo:
Against Elo:
K factor:
Win Draw Loss
Expected Percentage:

The Elo rating system is a method for calculating the relative skill levels of players in zero-sum games such as chess. It was created by Arpad Elo, a Hungarian-American physics professor and skilled chess player. Elo developed his rating system as an improvement over the earlier system used by the United States Chess Federation (USCF) during the 1950s and 1960s.

Here’s a brief history of the Elo rating system:

  1. Origins in Chess: The Elo system was originally devised as a way to improve the chess rating system in use by the USCF. The USCF had been using a numerical rating system for its members since 1950, but it was Arpad Elo who developed the system that bears his name, formalizing it in the 1960s. Elo’s system was adopted by the USCF in 1960.
  2. Adoption by FIDE: The World Chess Federation (Fédération Internationale des Échecs, or FIDE) adopted the Elo system in 1970. It quickly became the standard method used to rank chess players worldwide.
  3. Mathematical Basis: The Elo system is based on statistical estimation and probability theory. It assumes that the chess performance of each player in each game is a normally distributed random variable. The difference in the ratings between two players serves as a predictor of the outcome of a match.
  4. Expansion Beyond Chess: Although originally developed for chess, the Elo rating system has been adapted for use in many other competitive games and sports, including football, basketball, Major League Baseball, table tennis, board games like Scrabble, and video games.
  5. Online Gaming and Further Developments: With the rise of online gaming, Elo ratings have been adapted and modified for various multiplayer competitive games to match players of similar skill levels together. Different variants of the Elo system are used, for example, in games like League of Legends, Dota 2, and many others.
  6. Modifications and Alternatives: While the Elo system has been incredibly influential, various organizations and sports have made modifications to better suit their specific needs. For example, the Glicko rating system, developed by Mark Glickman, is a refinement of the Elo system that accounts for the volatility in a player’s performance. The FIDE also uses a modified version of the Elo system for its chess ratings.

The Elo rating system’s elegance lies in its simplicity and the ability to provide a clear, numerical value to represent a player’s skill level, making it an enduring and widely adopted method for ranking and matching competitors in various fields.