Understanding RPI

If you’re anything like me, the acronym RPI is something you’ve been hearing a lot lately, and it’s confusing. You don’t fully understand what it is, what it means, or how it works.

But, thanks to my uncanny thirst for more knowledge, I’ve done my research and I’m here to help you understand to the best of my ability. I can’t promise that you will grasp everything, but I am going to regurgitate my findings in better terms.

The Ratings Percentage Index, or what we have come to know as the RPI, comes into play for the playoffs — it determines initial seedings and matchups, but it also affects those down the road. Those seedings determine home field (or court) advantage as well. It’s not just for the playoffs, though, as it is affected by every matchup in the regular season for not only you, but your opponents, and their opponents.

I’m sure there is some analytical wizard sitting in a high castle somewhere that rubs his hands together looking at every playoff bracket in the country, saying to himself, “Yes! My very complicated algorithm is finally in use again!” Or it’s an accountant that loves sports so much that they devised this complicated math problem in a Microsoft Excel spreadsheet years ago and laughs every time it’s brought up, because of how hilariously intricate it is.

I know the latter isn’t true, because the RPI system has been in place since at least the 1980s, long before Excel was invented, but I’m not 100 percent sure that there isn’t an evil wizard laughing at us common folk as we scratch our heads and try to make sense of the complicated nature of playoff seeding and opponents’ opponents’ records. No, that is not a typo, where I accidentally put the same word twice. The system looks at your opponents’ records and their opponents’ as well.

The RPI system varies across sports and levels. For example, division 1 collegiate basketball doesn’t include games against schools that aren’t in division 1. That’s not really feasible in high school athletics, especially not here, because of the fluctuation in divisions across the area.

Collegiately, it is used to determine rankings for basketball, baseball, softball, hockey, soccer, lacrosse, and volleyball, and it used to help the seeding of the infamous “March Madness” tournament until fairly recently.

I will save you from the long, boring synopsis that I found on RPIRatings.com, as it discusses the different factors, the decimal points used, the weights of the games, and even factors that aren’t even used anymore. Instead, I’ll give you a shortened version, which in my opinion, explains it much easier.

The breakdown is as follows: your winning percentage makes up 25 percent of your rating, your opponents’ winning percentage makes up 50 percent, and their opponents’ winning percentage makes up the final 25 percent. The two factors that aren’t your own winning percentage make up your strength of schedule, which means 75 percent of your rating isn’t anything you can control.

For the same of demonstration purposes, I’ll give an example. These numbers are arbitrary, mean nothing, and don’t reflect an actual RPI rating, but are instead supposed to serve as a humorous, albeit informative, example.

Let’s say I’m the coach of the Ohio State Buckeyes’ basketball team. So far, I am 9-0. My opponents’ combined record is 0-81, and their opponents’ record is 41-40. My RPI rating would be .38, because it’s my winning percentage (100) times .25, my opponents’ winning percentage (0) times .50, and their opponents’ winning percentage (.51) times .25.

But, like I said earlier, this applies differently across sports and playing levels, so this formula doesn’t apply to every scenario.

You might be asking yourself if there are any pitfalls to this system, and the answer is yes. It doesn’t account for blowout wins, comebacks, playing opponents of higher or lower divisions (except in the case of NCAA basketball), or anything other than who you play. You cannot truly control your own destiny. Teams, especially in FBS football, are often said to have “cupcake” schedules, which do nothing but boost their RPI for the newly-expanded playoffs. Yes, that is a shot at every over-hyped SEC team, but my Buckeyes are “victims” of this all too often as well.

Now you’re probably asking yourself why this was even put into place to begin with, and the short answer is gambling. Someone could “fix” a game, like the Timothy Donaghy, an NBA referee who controlled point spreads for betting. Because the RPI excludes point differentials and scores, it eliminates this as a possibility, and makes cheating via gambling that much harder.

Of course, I didn’t go as in-depth as RPI truly is here, but I implore you to research it yourself and find out more about it; that will serve you better than anything I can write, because I don’t fully understand it myself. But, to the casual fan who just wants to know why their team got the seed they did in the playoffs this go-round, this should suffice.