Calculation of the Ninja rating list

1.The Ninja rating list is calculated from the results of all games from ChessNinja tournaments. Other games that are posted on the ChessNinja message boards can also be included, provided both players agree to the inclusion. Minimum time control is g/15 (15 minutes per player).

2.After  every game a performance rating for the current rating period (usually the current tournament) will be calculated for each player using the following formula:

                Perf = Opp + 800*(sc/gm_new - 0.5) ,

with Opp being the average rating of the opponents, gm_new the number of games and sc the achieved overall score in these games.  In case the opponent's rating prior to the game Ratg_Opp is larger than the considered player's rating Ratg_Pl + 400, or smaller than Ratg_Pl - 400, the average opposition rating will be calculated using Ratg_Pl + 400 (or Ratg_Pl - 400, respectively) instead of Ratg_Opp.

The new rating will be

                Ratg_new = (gm_old*Ratg_old + 1.25*gm_new*Perf) / (gm_old+1.25*gm_new) ,

with Ratg_old being the rating before the current rating period, and gm_old  the number of games played before the current rating period, but not larger than 20..

3.New players will enter the list with a rating of 1400 unless they supply an OTB or online rating that can serve as an estimate of their strength and will be used as an initial Ninja rating in that case.

4.A player who has not played any rated games in a year or more will be considered inactive. He/she will not be included in the ranking, but the rating will remain valid and become active again as soon as he/she plays at least one rated game again.