Rating Calculation

Longshanks uses tournament events from the past year when calculating and reporting data. You can use the “data filters” option that appears in the main menu on some pages to adjust which events and games are included on a page.


Player rating on Longshanks is based on the rating percentage index.

RPI = R/4 + OR/2 + OOR/4

R = win/loss record, OR is average R of all opponents, OOR is average OR of all opponents.

Game Threshold

Each game system has a threshold set by that game’s administrator. This threshold represents approximately half the number of games played by a typical competitive player per year.


To account for new and untested players, RPI is modified to favour more games being played. A Q-factor is calculated for each player based on the number of games played and the game system’s threshold.

The Q-factor is very large when a player has played a few games and disappears as a player approaches the game threshold.

Q = 1 + e ^ ( [10/T] * [T/2-N])

e = Euler’s number, T is the game threshold, and N is the number of games played.

The rating of a player who has played fewer games than the game threshold is calculated by dividing that player’s RPI by their Q-factor. Once a player has reached the game threshold, their rating is equal to their RPI.