The K factor in games
Notes
- K factor is used in ELO systems.
For a 2 player game the basic formula is: K/(1+10^((Ra-Rb)/400))
For more than 2 players, a single game is treated as a series of head to head matchups. The multiplier is adjusted downwards slightly, but I don’t know exactly what it is. I think with 3 players K is 75-80% of the 2 player value and for 4 player is 60-67%
K is as follows:
If you have less than 10 games played, K=60 (you win 30 points against a player with the same ELO).
If you have between 10 and 20 games played, K=40 (you win 20 points against a player with the same ELO).
Above 20 games played, K=20 (you win 10 points against a player with the same ELO).
change in rating = K * (result - expected)
# result - win: 1, draw: 0.5, lose: 0
# expected:
expected = 1 / (1 + 10^((opponent_rating - player_rating)/400))
184,69 K = 20 expected = 1 / (1 + 10^((120.77 - 130.1)/400)) = 0,51342372 0