Each player is given a few ratings when they create their account that represents skill level when compared to other players in the game.
The three ratings a player receives operate the same, the only difference is when a particular rating is reset.
The lifetime rating is never reset and signifies the overall skill level of the player since their account creation.
The yearly rating will reset at the end of the calendar year. (December 31)
The seasonal rating will reset when the in-game season has ended. Every 12 weeks on Mar 31, Jun 30, Sep 31, Dec 31.
Upon account creation you are assigned 3 ratings each starting at 1600, when you are paired up with another player and win, your rating will go up. If you lose against a player, your rating will go down. Your rating will change at the end of every round.
The amount your rating will change is based on the following formula:
An essential component to calculating your rating change is your Win Expectation, or Expected Win Percentage (EPW). Based on the difference between your rating and your opponent's ratings, the system calculates how likely it is that you will beat your opponent.
This is supposed to read 100 divided by 10 to the power of X plus 1. X is equal to the opponent's rating minus your rating then divided by 400.
In general, the wider the rating gap, the more often you should beat your opponent.
When playing someone at the same rating as you, you are expected to win exactly half of the time.
Calculating your rating change once you know your expected win percentage is easy. The only other factor taken into account when calculating your rating change is the Event-Value
The Event-Value of an event is tied to the competition level, so a 100 point game will have the lowest value at 8, while events with more starting points can change the Event-Value to be as high as 32.
You can calculate your rating change using this simple formula:
Win Value is just 0 for a loss, 0.5 for a draw, and 1 for a win.
Your new rating is calculated by adding your old rating to the rating change.
Other points of interest:
(1) The points you would win minus the points you would lose always add up to the Event-Value of the event. So if you would gain 1 point for a win against an opponent, you would lose seven against that same opponent.
(2) You will always lose points for a draw result against someone who has a lower rating than you.
(3) The number of points you win is exactly the same as the number of points your opponent loses, and vice-versa.
(4) Fractions of a point do matter. Even though the system reports show only your whole number of points we keep a running total of your exact rating to the fourth decimal place.