The Best NBA Teams Of All-Time, According To Elo

The stakes in the NBA are incredibly high. Superstar players so dominate the league that decisions on trades, draft picks and free-agent signings could gut a franchise for years or make it a perennial contender. But unlike in sports like baseball and hockey, where luck plays a larger role, in the NBA, the best team usually wins. There’s little forgiveness when a star player gets hurt, and when a team misses its first chance at a title, it may not get another.

We wanted a way to visualize each team’s ups and downs. You can find that in the form of our new interactive graphic, “The Complete History Of The NBA,” which tracks each franchise through all 63,145 games (and counting) in NBA and ABA history.²⁵

Elo ratings, the basis for the interactive, should be familiar to regular readers of FiveThirtyEight. We introduced them for the NFL last year, and they proved to be a popular feature.²⁶ But we didn’t invent the idea: Elo ratings were originally developed to rate chess players and have also been used in soccer, baseball and other sports.

Elo is like the iPad of sports power ratings: Their design is quite simple, and they do a lot with a little, depending only on the final score of each game and where it was played. Teams always gain Elo points after winning games — although more for upset wins and for winning by wider margins — and lose ground after losing them. They account for both regular-season and playoff games. If you want (much, much) more detail, see here. For the rest of you, here’s a quick guide on how to interpret different Elo ratings and about how many wins they’d translate into over the course of an 82-game regular season.

Elo ratings above 1800, which imply a team would be able to sustain at least a 67-15 record over the long term, are extremely rare. Only three teams have achieved them: the 1995-96 Chicago Bulls (whose 1853 Elo rating from June 9, 1996, is the all-time record), the 1996-97 Chicago Bulls and the 1985-86 Boston Celtics. This year’s Golden State Warriors have a chance at an 1800-plus rating, depending on how the rest of the playoffs go.

A 1700 rating is more typical for a title contender. The Cleveland Cavaliers, with a 1689, are currently somewhere near that mark, for example. A 1600 rating represents a playoff team that’s likely to lose in the first or second round. And Elo ratings can go way lower, of course. The all-time NBA low, 1111, belongs to the Dallas Mavericks after they went 4-57 to open the 1992-93 NBA season.²⁷

So where do, say, the 1982-83 Philadelphia 76ers rank? Here are Elo’s ratings of all seasons in NBA and ABA history:²⁸

You can sort the teams in several ways: by their season-ending Elo rating, by their peak rating or by their average rating throughout the season.²⁹ A team’s composite Elo rating is a simple average of these three.

For the very best teams — and I already mentioned some of Elo’s favorites, like the Jordan-era Bulls and the 1985-86 Celtics — the ratings are high across the board. The ’82-83 Sixers are another of these, ranking as the 10th-best team all-time.

But in other cases, there’s a pretty big difference between peak, year-end and average ratings. The 1999-2000 Los Angeles Lakers achieved the 11th-highest peak rating ever (1779). But their year-end rating is a pedestrian 1690 because they coasted down the stretch and then struggled (relatively speaking) in the playoffs, getting outscored by both the Portland Trail Blazers and Indiana Pacers despite winning those series. Conversely, the 1988-89 Detroit Pistons got better and better as the season went on, going 35-6 in the second half of the regular season and then 15-2 in the playoffs against opponents that included the Lakers, Celtics and Bulls.

The list might seem to be biased toward relatively recent teams: Among the top 50 seasons all-time, only six from before 1980 make the list. This is mostly a consequence of there being more teams than there once were. Simply put, it’s much more impressive to be the best team in a 30-team league than in a 10-team league.

But it’s also hard to say the NBA is watered down, at least right now. In fact, it’s barely expanded in recent years, adding just one franchise since 1995. That makes recent teams’ performances more impressive than those from, for example, the early 1970s, when the NBA almost doubled in size over a few seasons. When Elo ranks a team higher or lower than you might expect intuitively, it’s usually because it perceives the team’s competition to be especially strong or especially weak.

Some teams, meanwhile, do their damage over the long run instead of having any one standout season. The best team from the Celtics dynasty of the 1960s ranks only 47th all-time. But the Celtics of that era were incredibly consistent, with a composite Elo rating falling somewhere between 1627 and 1704 over 11 consecutive seasons. The San Antonio Spurs, meanwhile, have placed 13 teams in the all-time top 100 since 1994-95, but their highest-ranked individual season (2013-14) is only 12th.

And what about this season’s Warriors ranking as the fourth-best team of all time? Obviously, that’s a provisional score: They may rise or fall a couple of slots depending on how the rest of the playoffs go (although they almost certainly won’t pull ahead of the 1995-96 Bulls). But even though the conventional wisdom has been skeptical about the Warriors at times, we think Elo’s case is pretty easy to defend.

Here’s how it goes. As we’ve said, Elo is all about accounting for the strength of a team’s competition, and the Western Conference over the past dozen or so years has featured about the toughest basketball competition imaginable. The Warriors’ 67-15 regular-season record is as good as any other Western Conference team from this era, and their regular-season point differential (+10.2 points per game) is better than anyone else’s. If they follow that up with a title, there really won’t be much to find fault with. Whether they’re a one-year wonder or will prove to be a perennial contender is another question, of course. We hope you’ll enjoy exploring the interactive and tracking their progress.