Match Rules
101 Weiqi defines 19 levels from 10 kyu to 9 dan. Each level is determined by rating; when your rating reaches the required range, the corresponding rank is displayed.
*Changes to the 101 Rating use the internationally popular Elo rating system.*
The following is adapted from Wikipedia.
The Elo rating system was created by Hungarian-American physicist Arpad Elo to measure skill in competitive activities. It is now a widely recognized method for evaluating playing strength and is used in chess, Go, football, basketball, and many other sports. Competitive systems in online games also use similar ratings.
Elo is a statistical method for estimating a player's strength. The United States Chess Federation first adopted it in 1960. Because it was fairer and more objective than earlier methods, it quickly became popular, and FIDE formally adopted it in 1970. The original Elo model used a normal distribution, but practical results showed that player performance did not follow one closely, so modern systems commonly use a logistic distribution.
Calculation
Suppose players A and B currently have ratings R_A and R_B. Under the logistic distribution, A's expected score against B is calculated from the difference between those ratings, and B's expectation is calculated in the same way.
If a player's actual score S_A in a game—1 for a win, 0.5 for a draw, and 0 for a loss—differs from the expected score E_A, the rating is adjusted accordingly.
R_A and R_A′ represent the rating before and after adjustment. In master-level competition, K is commonly 16.
For example, Player A, rated 1613, draws with Player B, rated 1573. If K is 32, A's expected score is approximately 0.5573, so A's new rating is:
1613 + 32 × (0.5 − 0.5573) = 1611.166
The 101 rating system uses K = 10 and discards the decimal portion. It also includes adjustments for handicap games.