ELO System

[Ravtar]

Dear BGA team,
It's always a real pleasure to play on BGA !
I have a question/remark about the ELO system. When I play a game with some other players with equivalent ELO and when I loose the game (it arrives sometimes ), I loose a lot of ELO points... But when we win, we win a few ELO points. I think it's not "normal"...
How the ELO points are calculated ?
Thanks a lot,
And "Longue vie à BGA !!"
Fred

[RicardoRix]

In the game results page you can hover over the players ELO score to get a display of exactly how it's been calculated.
Power to the People.
-Woolfie.

[dschingis27]

When I play a game with some other players with equivalent ELO and when I loose the game (it arrives sometimes ), I loose a lot of ELO points... But when we win, we win a few ELO points.

This is actually impossible. When you play against opponents with Elo value roughly equal to your own Elo value, you'll gain ~10 points if you win, and you will loose ~10 points if you loose (in a 2p game). The absolute Elo change will be similar between winning and loosing if you play against opponents close to your level. If you have counterexamples, I would be very surprised. But of course you gain only few Elo when you win against players with Elo level far below your own Elo.

In gerneral, go to the FAQ and wikipedia to learn about the Elo System (it actually emerged from a guy whose name is Elo). And if you have fun collecting points, then play Arena Mode.

[admitted]

Difference of ELO (not actual elo) gives implied probability of winning a Head to Head match. Then depending on k-factor (arena 2p is 38.6, live game 2p is 20, different for 3/4/5p as well), you will gain ELO for win, tie, or lose.

Implied probability has a formula and it comes out like this:
https://walkofmind.com/programming/chess/elo.htm

[Xiuhcoatl]

I think Fredo1978 is referring to games with more than two players, and indeed I have made similar observations. See for example this recent game: https://boardgamearena.com/table?table=125812312

I won against two opponents of similar ELO (all in the range 150-200), and when I hover above the ELO change to see the details of the calculation, I get roughly +9 points for each opponent, as expected for a K-factor of 20. But in the total sum, I only get +9 ELO for the victory, instead of +18 as I would have expected! However, the player to come in 3rd receives a total ELO delta of -28 (from 2x(-14) at a K-factor of 30).

I looked at a few other games I played with more than two players, and similar effects appear often, but not always.

This can be quite annoying, and it seems to be at odds with the FAQ: https://boardgamearena.com/faq?anchor=faq_account_elo

[Tulivuori]

Multiplayer elo works differently in bga when you have a low amount of games played than when you have a high amount. But I think no one from bga has ever explained why it's like that or how it exactly works.

[AlvaroJL]

hi Fredo.
I think fredo is right.
The answer to your question is: The ELO than you win or lose depends of how many opponents play with you. And in FAQ are wrong. Better the answer is incomplete. The system calculate your ELO like they explain in FAQ. But you don't receive or lose the total of the ELO. That depends of number of players. I'm not sure how is the formula, But is similar to this: For two players (100% ). For three players (75%). For four players (66%). For five players (62.4%). For 6 players (50%). It is correct if your K factor is 20. If your K factor is 27 or 40, you receive the 100%. I'm not sure if you lose (100%) too.

In other words. Your ELO depends of this factors: K factor, The difference between you and each opponent, and the amount of players in the table.

[whatshisbucket]

The constant multiplier Alvaro describes depends not only on the number of players, but also on the game, the latter of which is a bit of foolish implementation (although those values [1, 3/4, 2/3, 5/8]) are fairly common).

[ufm]

Dear BGA team,
It's always a real pleasure to play on BGA !
I have a question/remark about the ELO system. When I play a game with some other players with equivalent ELO and when I loose the game (it arrives sometimes ), I loose a lot of ELO points... But when we win, we win a few ELO points. I think it's not "normal"...
How the ELO points are calculated ?
Thanks a lot,
And "Longue vie à BGA !!"
Fred

I think Fredo1978 is referring to games with more than two players, and indeed I have made similar observations. See for example this recent game: https://boardgamearena.com/table?table=125812312

I won against two opponents of similar ELO (all in the range 150-200), and when I hover above the ELO change to see the details of the calculation, I get roughly +9 points for each opponent, as expected for a K-factor of 20. But in the total sum, I only get +9 ELO for the victory, instead of +18 as I would have expected! However, the player to come in 3rd receives a total ELO delta of -28 (from 2x(-14) at a K-factor of 30).

I looked at a few other games I played with more than two players, and similar effects appear often, but not always.

This can be quite annoying, and it seems to be at odds with the FAQ: https://boardgamearena.com/faq?anchor=faq_account_elo

Yesterday I posted a suggestion regarding this, so please check it out and upvote it if you're interested in!
https://boardgamearena.com/bug?id=29568