What is Elo Rating System?

The Elo rating system is a method of calculating the relative skill levels of chess players, devised by Hungarian-American physics professor Arpad Elo (1903–1992). FIDE adopted the system in 1970. A player's Elo rating increases with wins and decreases with losses, with the magnitude of change depending on the rating difference between the players. Higher-rated players gain fewer points for expected wins and lose more for unexpected losses. The system is used in many other competitive contexts beyond chess.