This is a documentation for Board Game Arena: play board games online !

# Rating

## What is ELO rating ?

Your ELO rating for a game is your level at this game. It's a 4 digits number followed by sign .

Example: 1648 .

If you never play a game on BGA, your initial rating is 1500 . Each time you win a game your rating increases, and it decreases each time you lose a game.

## How many points do I gain / lose for each game ?

ELO points gains / losses depend on the level of your opponents, and your rank at the end of the game. Some examples:

- If you end the game in a better position than a player with a higher ELO, you gain a lot of points.
- If you end the game in a better position than a player with a lower ELO, you gain fewer points.
- If you end the game in a worse position than a player with a lower ELO, you lose a lot points.
- And so on...

## Some advice

- There's no use beating players a lot weaker than you (not many points to win). Try to find opponents of your level: it's both more fun and better for your ELO.
- Game rank is very important when calculating the ELO. This is the reason it is important to continue fighting for minor places in the game even if you think you can't win.
- The number of ELO points you can gain/lose during a game increases with the number of players. The maximum is reached when there is the "recommended number of players". Try to play games with this recommended number of players.
- When you are the first player to quit a game in progress you lose as many points as if you had finished the game in last place, plus an additional penalty of 10 points. Even if you are in a difficult situation it is in your interest to play the game until the end - or concede the victory to your opponent.

## How is my ELO ranking computed ?

The BGA ELO system is directly based on the standard ELO rating system, in use for chess.

The ELO system's main principle is the following: the ELO points difference between 2 players determines the probability of each of them winning an encounter. If two players have the same ELO, they have an equal (50/50) probability of winning. If one player has 400 more points than the other, his probability of winning is 90%. ELO points gains and losses will, over time, tend to adjust the ELO rating of each player to reflect the actual probability that either of them will win a particular encounter.

Some changes have been made to the ELO system used on BGA:

- During your first 30 games, your ELO rating is more "elastic": you can win (or lose) more points in each game. This way, your ELO rating converges faster to you "natural" rating.
- The original ELO rating system was designed for 2 player games. For games with more than 2 players, BGA considers (for the ELO rating) that you win a 2-player game against each opponent below you (in game rank) and that you lose a 2-player game against each opponent ahead of you (in game rank).
- Games with more than 2 players last longer. For this reason, there are more points to win (or lose) in such games... as long as the number of players does not exceed the "advised number of players" for that game.

## Okay, but I want to know the formula !

The formula is exactly the one used by the ELO rating system, with the following adjustments:

- First of all, if someone leaves a game for any reason this game is not taken into account by the ELO rating system.
- K=60 for the first 30 games, K=40 afterwards.
- K is multiplied by (N/2) for N-player games. If N exceeds the "advised number of players" for this game, K is multiplied by (A/2), where A is the "advised number of players".
- If 2 players have a rating difference greater than 600, we consider that their ELO difference is 600.

## Good players, Experts, Masters

- Good players: > 1600 ELO
- Experts: > 1800 ELO
- Masters: > 2000 ELO