Skill Ratings

The Basics

Case's Ladder uses a modified version of the rating system used by major chess groups. These ratings systems are unique because they are considered "zero-sum." This means that when you win a game, your rating will increase a certain number of points. Your opponent loses the same number of points that you gained. If you lose a game, the reverse will happen: You will lose as many points as your opponent gains. The number of points that you gain or lose depends on the ratings of both players involved.

If you rating is higher than your opponent you will not gain as many points as you would have by playing someone with a higher rating than you. If you lose to someone who is rated less than you, you will lose more points than you would have gained had you won the match. This is a method for automatically handicapping players.

Formulas

The following formula is used to calculate ratings:

Rn = Ro + K(W-We)

Rn = The new rating for the player
Ro = The player's old rating
K = Numerical constant (30 for established players with over 50 games played, 50 otherwise)
W = If the player won the match, this value is equal to 1, otherwise it is zero.
We= The expected result of the game based on the following formula:

We = 1/ (10^(-dr/400) + 1)
(dr is equal to the difference of the players' ratings)

NOTE: New players start with a rating of 1500.