ELO rating system: value of K

[Blip Blop]

I'm trying to figure out how the elo system of BGA works. I read this BGA wiki page: http://it.doc.boardgamearena.com/Rating. I can't understand which is the value of "K" in the last formula ( Rn = K.P + (1-K).Rp). Can you help me, please? Thanks!

[sprockitz]

That formula isn't accurate, so you can just ignore it. I'm not sure if it was ever used, but definitely isn't how Elo is calculated these days.


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).

[Blip Blop]

Allright, thank you. There was something that didn't make sense to me, in fact.

I'm confident with the ELO system 1vs1, but I don't know how it works with more player. Can you just tell me in a simple way which passages and formulas should I use in addition to the basic ones of the classic ELO system? Thank you!

[demiurgsage]

if a game is played with more than two players then every result will be multiplied by N/(2 * (N-1)), N - number of players if N is equal or less than recommended number of players. if N is more than recommended number, the multiplication factor is (recommeded N)/(2 * (N-1))

[sprockitz]

if a game is played with more than two players then every result will be multiplied by N/(2 * (N-1)), N - number of players if N is equal or less than recommended number of players. if N is more than recommended number, the multiplication factor is (recommeded N)/(2 * (N-1))

Thanks!

So assuming recommended N is equal or greater...
N = 3, => 75%
N = 4, => 67%