How are the ratings calculated?

On Chess-Mind.com, you are rated accordingly to Elo rules

To evaluate everyone's level, each player has her/his own Elo score.
This score can vary from 1015 to more than 2800 points.
The Elo and the glicko systems are the more widely used rating systems ; but since we wanted to use the same rating system that the one in use at the FIDÉ, we chose Elo.

How does it work ?

The overall principle is quite simple : when you win a game, you get points and when you lose a game, you lose points...
The number of points you can win or lose vary accordingly to the difference between the opponents.
If you are currently rated lower than your opponent and still win the game, it will bring you more points than if you were rated higher.

For instance, John has 2234 points and Marc 2456.
If John wins, his victory being quite a feat, he'll get 19 points and Marc will lose 19 to compensate.
If Marc gets the upper hand, his victory was more predictable since he was already rated higher than John, so he will only win 5 points and, for the same reasons, John will lose 5 points.
If they manage to do a draw, John will still have 7 points — and Marc will lose the same amount.
You can refer to the mathematical formula to know the exact amount of points pending for a game.

Note : Chess-Mind.com ratings has to rate a maximum of players in order to be more accurate : We need your help for this!

Colors and levels

We chose to assign a level and a color for every Elo range of points ; with the help of this indicator, you will be able to see the expertise of a player at a glance, and thus choose wisely your next opponent.

• Unclassified : less than 8 games played
• Beginner : less than 1199
• Occasional Player [Class D] : 1200 to 1299 Elo points
• Occasional Player [Class C] : 1300 to 1399 Elo points
• Occasional Player [Class B] : 1400 to 1499 Elo points
• Occasional Player [Class A] : 1500 to 1599 Elo points
• Experienced Player [Class D] : 1600 to 1699 Elo points
• Experienced Player [Class C] : 1700 to 1799 Elo points
• Experienced Player [Class B] : 1800 to 1899 Elo points
• Experienced Player [Class A] : 1900 to 1999 Elo points
• Advanced Player [Class D] : 2000 to 2099 Elo points
• Advanced Player [Class C] : 2100 to 2199 Elo points
• Advanced Player [Class B] : 2200 to 2299 Elo points
• Advanced Player [Class A] : 2300 to 2399 Elo points
• Master : 2400 to 2499 Elo points
• Chess-Mind Master : 2500 to 2799 Elo points
• Chess God : more than 2800

The first one to reach the highest mark of the ratings with a score greater than 1999 will see a star ( ) in front of her/his name!

Elo Formula

After each official game, Elo scores of both players are updated using this formula :

With, for each player :

• dE : pending Elo points
• S : Score (1 = won, 0 = lost, 0.5 = draw)
• F : F factor (rating disparity) = 400 : the higher is F, the easier it is to gain points (or to lose them)
• D : Score difference : Player Elo score - Opponent Elo score
• K : K Factor (game importance), computed as stated below :
  • The score of one of the players is < 2100, K will be 32
  • The score of one of the players is < 2401, K will be 24
  • Both players have a score > 2400, K will be 16

A few things to know...

• A practice game doesn't influence the ratings
• Everyone starts with a score of 1450 points
• You enter the rating list after your 8^th game
• Nobody can go below 1015 points

Source : http://en.wikipedia.org/wiki/Elo_rating_system