How Ratings Work

How does rating change after matches?

Your rating can go up or down after each recorded match.

• If you beat a higher rated player, your rating usually goes up more.
• If you lose to a lower rated player, your rating usually goes down more.
• If the result is expected, your rating usually changes only a little.

What is "confidence"?

Confidence is how sure the system is about a player's rating. On this site it is shown as High, Medium, or Low.

• Low: not much information yet (for example, few matches). Ratings can move faster.
• High: lots of information. Ratings usually move more slowly.

Why does confidence affect the number shown?

The rating displayed on this website is a cautious estimate. If confidence is lower, the number shown is slightly lower to avoid overrating players when the system is not sure yet.

Technical Details (Glicko-2)

Extra details (not needed for normal use):

• The system is based on the Glicko-2 rating system. Wikipedia: Glicko rating system
• Under the hood each player has three main values: rating, RD (rating deviation), and volatility. RD is uncertainty (higher means "less sure").
• The number shown on the website is a conservative rating: round(rating - RD). This is like a lower bound when the system is uncertain.
• The confidence label is derived from RD: High if RD <= 80, Medium if RD <= 150, otherwise Low.
• New players start at rating 1500, RD 350, and volatility 0.06.
• Match results are converted into a single outcome per match: win = 1.0, draw = 0.5, loss = 0.0.
• If a player does not play for a while, RD tends to go up, which lowers the conservative rating until more matches are played.