What is RPI in Basketball?

Last updated on October 25th, 2023 at 07:52 am

The RPI in basketball is also known as the rating percentage index / relative percentage index, and it ranks teams. This ranking details the team’s wins and losses compared to the team’s strength of schedule. The RPI in basketball also considers the team’s average opponent’s winning percentage.

How Do You Calculate Basketball RPI?

First, you take 25% of the team’s winning percentage. Next, take 50% of that team’s opponent’s average winning percentage (OWP). The third step is to take 25% of the winning percentage of their opponent’s opponent (OOWP). Lastly, you will want to add all of those percentages up. The number you come up with is that team’s RPI.

Check out the example below with fake numbers to see how to calculate the RPI for a basketball team.

An Example of How the RPI Formula Works in Basketball

Let’s pretend that you want to figure out the Boston Celtics RPI. The Boston Celtics have an 8-2 record, their opponent (LA Lakers) is 5-5, and their opponents have a 52-18 record.

The Boston Celtics have a (.8 win percentage), the Lakers have a (.5 win percentage), and the opponents against the Lakers have a (.74 win percentage), taking those numbers above.

RPI for the Boston Celtics = (.25*.8)+(.5*.5)+(.25*.74) = .63

Is a Higher or Lower RPI in Basketball Better?

Generally speaking, a low RPI indicates that a team is struggling to win games. Likewise, a high RPI shows that a team is winning games. However, if a team is in an easier division than another, further analysis is necessary to review teams against each other.

RPI calculations are essential for two main reasons. One of those reasons is that this calculation will show you a combined winning percentage. The other reason is that the RPI will allow you to compare that team to other teams in the same division. For instance, if you know the RPI of all Division I teams, you will easily be able to compare those teams.

But how should you go about making that comparison? Start by looking at the RPI of each team and determining which team has the highest RPI. For instance, if Michigan has a 0.66 RPI, they are doing twice as well as Indiana, which has a 0.33 RPI.

How Is RPI Calculated in College Basketball?

RPI is among the most popular ranking systems in college basketball today. It is a metric that quickly points out the most successful teams of the season. However, someone has to do the calculations to figure out a team’s RPI.

As mentioned above, start by taking 25% of the team’s win percentage. Then, take 25% of the OOWP and, lastly, take 50% of the OWP as it pertains to the basketball team in question. Add all three of those figures together, and you will end up with the team’s RPI. This is the formula for NBA RPI and general RPI.

However, there is an extra step for calculating the RPI for college basketball. When calculating the team’s win percentage, you must factor the team’s home wins and losses by 0.6. Then, you will need to factor the team’s road wins and losses by 1.4. It adds a few extra calculations, but the formula is still very manageable.

Does the NCAA Still Use RPI?

The NCAA still uses the RPI ranking system to provide a valuable tool to compare the different teams in the league. However, during the NCAA seeding process and men’s basketball tournament selection, the NCAA replaced RPI with the NET rating.

This replacement has been the case since 2018 and is the case in both Division I men’s basketball and women’s basketball. Since 2018, the NET has been used as an NCAA evaluation tool by the selection committee to rank the teams, which is essential when it comes time for tournament selection.

What is the Downside of RPI in Basketball?

One major downside to solely relying on RPI is that it doesn’t distinguish the degree of a game or games won for a basketball team. For instance, RPI will only factor team’s wins and losses. However, one team who wins games by an average of three points and another that wins by 20 points with the exact record get the same win credit in the RPI formula.

If, in that scenario, we assume that both teams have the same record for 40-8 and the other two factors in the formula are relatively close, then the RPI for both teams will be similar. However, the one team that consistently beats opponents by 20 points might be the more dominant team, but the formula does not recognize that.

To get the most out of RPI, you should combine that with additional metrics to evaluate basketball teams to get the complete picture.

Conclusion: What Is RPI in Basketball?

In conclusion, RPI stands for “rating percentage index / relative percentage index” and ranks teams in the regular season. This ranking is based on a team’s wins and losses compared to the strength of that team’s schedule. Calculating the RPI is relatively simple, though a few adjustments need to be made when calculating the RPI of an NCAA team.

However, it is essential to remember that the NCAA no longer uses the RPI for any official ranking. Instead, the NET ranking is what the NCAA uses to rank teams. While the NET considers the same factors as the RPI, it also considers several additional factors. The NCAA does still encourage the use of RPI for general comparison, however.