Competition, history, and culture
Ratings and registration
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Elo
A numerical system that estimates competitive strength from a player's results against rated opponents.
Performance rating
Performance rating estimates the rating level represented by a player's result in a specific set of games against opponents of a given strength.
Live rating
A live rating is an in-period estimate that incorporates recent results before those changes appear on the next official published rating list.
Provisional rating
A provisional rating is a temporary strength figure used before an official or established rating exists, but its exact meaning depends on the system using the term.
Initial rating
Level: IntermediateThe first playing-strength number that FIDE officially publishes for a previously unrated player.
Unrated player
Level: BasicA player who has no published rating on the particular list and time control used for the competition.
Inactive player
Level: BasicA player who keeps a FIDE rating but has played no rated games for one year.
Rating floor
A lower limit that a rating system places on a rating or uses as a minimum value for a specific calculation.
Development coefficient
Level: AdvancedThe multiplier controlling how much a FIDE rating changes when actual results differ from expected results.
Scoring probability
Level: AdvancedThe fraction of a point the rating system expects a player to score from a given rating difference.
Official FIDE Rating List
The recurring publication that establishes FIDE's official ratings and replaces the preceding list.
Rating period
Level: IntermediateThe interval during which an official rating list is valid and whose accepted results feed the next list.
FIDE ID
A FIDE ID, or FIN, is the unique number identifying a player registered by the International Chess Federation (FIDE).
