Starcraft 2′s Battle.net Leagues, Ladders, and Rankings Explained

Posted by on August 4, 2010 - 32 Comments »

Starcraft 2 has one of the most robust systems for ranking players of all skill levels and giving them fair games and a sense of progression. Blizzard doesn’t want to reveal too much detail about the way the rankings work as to prevent gaming of the system, and as such, a lot of speculation has caused a lot of misunderstanding among the player base. Still, we know that the ladder system is based around a few core principles and we have a lot of information that can be pieced together, so let’s examine the inner workings of the ladder system.

First, let’s tackle something a lot of people don’t know: the only thing that affects your ranking is winning or losing. Any good rating system for a competitive game must operate in this way. If it was based on how long the match takes, actions-per-minute (APM), or other factors, players could easily inflate those numbers to artificially increase their rating. Like ELO, the chess rating system on which Blizzard’s rating systems are based, each player has an associated number representing their skill level. In addition, there is an important second statistic called volatility that represents the algorithm’s confidence that your matchmaking rating (MMR) is accurate. This innovation allows players to be ranked very quickly and jump right into a range close to their skill. In other systems, like Warcraft III and even WoW’s arena system (to a degree), players must start at the bottom and work their way upward. The Starcraft 2 system prevents “n00b stomping” by creating new accounts and other abuses.

If you’ve tried the Starcraft 2 multiplayer, you are familiar with the process of acquiring a ranking. It asks you if you first want to play some practice games, which are played on a slower speed with “no rush” rules enforced. It is unclear if this data is incorporated into your early MMR, but I suspect that it is, as there is no drawback to starting players with an accurate rating. You then play 5 “placement” matches, where it chooses opponents from across the spectrum to try to get a general idea of your MMR. Keep in mind that it is only looking at win/loss data, and there are a lot of variables that go into deciding victory in a Starcraft 2 game. As such, with just five data points, the MMR it approximates for you is going to have a very high volatility.

Another key point to keep in mind going forward is that MMR is the sole factor in determining your opponents. League, rank and other factors have absolutely no hand. A high-ranked silver player could be playing a low ranked platinum player. If you have recently played an opponent, the system may shy away from matching you with them again, but this is just a theory I have carried over from Warcraft III’s matchmaking system.

With an MMR now associated with a new player, Battle.net will place players in a league. While your MMR is always hidden, the system seems to use only this number to place players into leagues. There are 5 leagues that players can be placed into, and in descending order of quality and approximate player base, they are:

  • Diamond (top 10%)
  • Platinum (10-25%)
  • Gold (25-45%)
  • Silver (45-70%)
  • Bronze (70-100%)

The system will never place a new player into the Diamond league after their placement matches.

Within each league are divisions. Each division is a small group of 100 people against whom members are ranked against. For example, one of my 2v2 teams is in the Gold Mutalisk November division. I can see all of the other players in this division, which gives me a ballpark idea of where I rank globally, but I do not play anyone in my division more or less than anyone else close to my MMR. The purpose of the division is simply to give players a sense of progression with a number that has less variance and more weight than a global ranking six digits long.

There are certain points at which Battle.net re-evaluates your league placement. The number of games or time-frame is not disclosed, but occasionally after a game, you will be placed into a new league. This can even occur after a loss. Players can be promoted or demoted to higher or lower leagues based on their performance. This is the only way to access the diamond league, as the system does not want 5 data points adding players into Diamond only to quickly remove them. Diamond status should be an “elite” league and carry some weight. During the initial rush of unranked players that occurred in the past week since release, the system has had very little data and, in my limited experience, low accuracy. My placement matches put me in the silver league, but after about 25 games, I’ve been promoted to gold and then to platinum, where I’m holding the top 10 in my division pretty well.

Now, how does your MMR change and how does this relate to points? We will explore this later this week with lots of number crunching.

Continue to part 2…