Elo ratings have a simple formula; the only inputs are the final score of each game, and where and when it was played. Teams always gain Elo points for winning. But they get more credit for upset victories and for winning by larger margins. Elo ratings are zero-sum, however. When the Houston Rockets gained 49 Elo points by winning the final three games of their Western Conference semifinal during this year's playoffs, that meant the Los Angeles Clippers lost 49 Elo points.

A rating of 1500 is approximately average, although the league average can be slightly higher or lower depending on how recently the league has expanded. (Expansion teams begin with a 1300 rating.) Select a team above, and zoom in to explore its history.

It's no surprise that the 1995-96 Chicago Bulls — with an NBA-record 72 regular-season wins — have the best Elo rating ever. The team picked up its fourth NBA championship at the end of that season, but the Bulls hit their peak Elo (1853) a few games earlier when they stomped the SuperSonics 108-86 in Seattle to take a 3-0 lead in the finals and improve their playoff record to 14-1. Chicago went into a "slump" for the next two games — losing both by double digits — before clinching the title in Game 6.