FIDE Online Arena Ratings
The Arena rating system is based on the FIDE rating regulations with slight necessary adoptions because of the differences between online and over the board chess. For example, the nature of online ratings require that a game is rated immediately after its completion. Also, a player is able to complete an unusual high number of games while enjoying his/her living room comfort. However, the conclusion that a player's performance is irrelevant to the medium, but is related to the time control, lead FIDE to the revolutionary decision of providing ratings which combine online and over the board game results.
FIDE Online rating regulations use the abbreviation "RBB regulations" to distinguish from FIDE rating regulations for rapid and blitz. Bullet chess is not defined in FIDE's Laws of Chess. This is the reason why Arena rated games are played with pre-defined time controls, 4 of which are used to construct the Bullet online rating list. Pre-defined time controls serve another purpose as well. They allow a variety of thinking time choices with or without increment and the total chaos from free choice bizarre time controls is avoided.
FIDE Online Arena ratings do not influence over the board game activity and the monthly FIDE rating lists for rapid and blitz over the board games. On the contrary, rating changes from over the board rapid and blitz games are included in FIDE Online ratings, once every month, as soon as the FIDE monthly rating lists are published. In this way, FIDE Online ratings reflect a player's overall activity, online and over the board alike. FIDE Online championships and special events where players are qualified by their rating are going to use the FIDE Online rating lists. Since online games are rated as soon as they are completed, there will be special announcements about the date and time used for player rankings.
The Online rating formulae are exactly the same with the ones used by FIDE for over the board games, based on the system proposed by the American Professor Arpad Elo. The conversion tables are the same, the K factor used for rapid and blitz is the same and equals to 20. However there are some notable differences. Bullet K factor equals to 10. FIDE Online server uses internally a 2-digit decimal accuracy although ratings are displayed rounded to the nearest integer. This measure replaces the 400-point rule used in over the board games, to minimize 1 point wins against a player with significantly lower rating. The online rating floor is only 100 Elo points instead of 1000 points in order to allow children and novice players to compete against opponents of the same playing strength.
A player's first rating is either determined by the player's rating in over the board chess or is calculated by the player's first 5 online games, the very first of which has to be either a drawn or a won game. 5 initial results plus a K factor equal to 40, allow a player to reach his/her actual rating by playing chess online. The same method of calculating first ratings are also used by the FIDE rating system for over the board chess.
The FIDE Online rating system is constantly being monitored by FIDE's Online Commission in order to determine ratings abuse or individual cases where ratings do not reflect the player's actual playing strength. In order to secure flexibility and have necessary changes and adoptions approved in a short period of time, Online Commission's proposed regulations need to be confirmed by the regular FIDE Presidential Boards, not the General Assembly which takes place only during the chess Olympiads.
The complete FIDE Online Arena rating regulations (RBB regulations) can be found here.