Halo Reach Arena Rating

rating = loss_penalty * (1000 + (2000/pi * atan( raw_rating * game_normalization ))) raw_rating = (kills + sa*assists) - (sd*deaths + sb*betrayals) game_normalization = players_per_team / score_to_win

The lowest (worst) theoretically possible Game Rating is 0, and the highest is 2000. The highest possible Rating in Slayer Arena in the Beta is 1844.

beta values
sa = 1.0 # assists are as good as kills sd = 1/3 sb = 1

score ranges is 0 ~ 2000, where 1000 is baseline

Divisions
These are the Divisions in the Beta...

5 = Onyx (best) 4 = Gold 3 = Silver 2 = Bronze 1 = Steel (worst)

So if I keep getting a high Game Rating, I'm going to be put in Onyx, right?
Not necessarily. All that matters is how your Game Rating compares to everyone else's Game Rating in a single game. It doesn't matter whether you have the highest Game Rating with a score of 1800 or the highest Game Rating with a score of 1500. Both will have the same impact on your rank.

If you have a Game Rating of 1750, and someone else has a Game Rating of 1751, your rank is going to be negatively impacted from having a lower Game Rating than that person above you.

There's likely to be a correlation between constantly getting high Game Ratings and getting a high Division, though.


 * http://www.bungie.net/Forums/posts.aspx?postID=43960065

assists
The number of kills you assisted a teammate with. In Reach, an assist is defined as "doing 40% or more of the damage required to kill a target that dies to other causes before a shield recharge can occur."

loss_penalty
If your team loses, this is a penalty applied to your rating.

But wait, you protest: "Isn't the Arena about individual performance?" It is, so our goal is that this penalty is as small as possible while still accomplishing two goals:


 * 1) Assuming equal performance, a player on the winning team should place ahead of his counterpart on the losing team.
 * 2) Playing for a personal best rating should require winning. No hanging your team out to dry to shoot for a high score.

For the Public Belta, this number is 0.96. In other words, if you lose, we shave a mere 4% off of your rating. We will be continuing to adjust this number, and we might even shift the place where this penalty is applied.


 * Taken from http://www.bungie.net/News/content.aspx?type=topnews&link=BWU_043010