Elo rating guides
How rating systems work, written to be read in a few minutes. Every fact links to the rule book, paper or official page it comes from.
What is the Elo rating system?Where Elo came from, the formula in plain English, and what a rating gap means.How to choose the K-factorFIDE, US Chess, FIFA and FiveThirtyEight values, and how to choose K for your own league.Elo vs Glicko-2 vs TrueSkillWhat rating deviation, volatility and team skill add, and when plain Elo is enough.Chess.com vs Lichess vs FIDE ratingsWhy the same player has three different numbers, from the sites' own documentation.Elo in sports and esportsFIFA rankings, NFL forecasts, Xbox matchmaking and AI model leaderboards.Elo for ranking anythingPairwise comparisons, office ping pong ladders and matchmaking, with practical settings.Elo FAQShort answers to the most common questions.