K-factor
The K-factor is the multiplier in an Elo-style rating update that sets how many points a rating can move after a result; a larger K makes the rating react faster.
Also called: K factor
After a game or event, an Elo-style system compares your actual score with the score your rating predicted, and the K-factor scales the gap. With K equal to 20, scoring one point more than expected adds 20 points. With K equal to 10, the same surprise adds only 10.
FIDE sets K by status (Rating Regulations, clause 8.3.3): 40 for a player new to the list until they have completed events totalling 30 games; 20 while the rating stays under 2400; 10 once the published rating has reached 2400, even if it later dips below; and 40 for any player, until the end of the year of their 18th birthday, while their rating stays under 2300. The same clause caps K times the games on a list in one rating period at 700 and lowers K where that product would be exceeded.
US Chess does not use a fixed table. Its published method sets K to 800 divided by the sum of an effective game count and the games played in the event, so K falls smoothly as evidence accumulates, with different rules for some high-rated players in dual-rated events.
The logic is simple: a rating with little evidence behind it should move quickly, and one backed by hundreds of games slowly. That is why juniors and newcomers swing more than long-established masters. Read provisional rating, rating performance and FIDE rating next.
A neighboring idea is Elo rating. An Elo rating is a number that estimates playing strength from results: the gap between two ratings predicts the expected score, and wins and losses move each player's rating up or down.
How "K-factor" applies to your own results depends on where you stand now, and the improvement plans by rating band show what players near your rating work on.
Related terms
An Elo rating is a number that estimates playing strength from results: the gap between two ratings predicts the expected score, and wins and losses move each player's rating up or down.
A FIDE rating is the Elo-based number that the World Chess Federation publishes each month for players with rated games, with a published minimum of 1400, and it is the rating that FIDE titles are measured against.
A provisional rating is an early estimate of strength built from only a few games, which is allowed to move quickly until enough results exist to make it reliable.
A rating performance is the rating a player seems to have played at in one event, found by adding a score-based adjustment to the average rating of their opponents.
A rating system is a method that turns game results into a number for each player, rising after wins against strong opponents and falling after losses, so that strength can be compared.
Guides that go further
What a rating measures, how FIDE, Lichess, US Chess and chess.com compute theirs, and why the numbers differ.
Average chess rating and a good chess rating
What share of active Lichess players are rated above 800, 1200, 1500, 1800 or 2000, by time control.
The Handbook rules for a first FIDE rating: five rated games, the 1400 floor, the two 1800 draws and a worked example.
Sources
- FIDE Handbook B.02 FIDE Rating Regulations, effective 1 March 2024, Clause 8.3.3, read Oct 21, 2026.
- US Chess, The US Chess Rating System (Glickman and Doan), dated 6 April 2026, Section 4.2, read Oct 21, 2026.
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