In college basketball, the selection of teams and determining where they are placed once there involves a mathematical calculation called the Rate Percentage Index (RPI).

The RPI is a metric used to compare the performance of teams against each other, primarily focusing on winning percentage. It takes into account a team’s record, the record of their opponents, and the record of their opponents’ opponents.

The RPI Formula

The RPI formula is as follows: RPI = (WP x 0.25) + (OWP x 0.50) + (OOWP x 0.25)

Where:

  • WP = Winning Percentage
  • OWP = Opponents’ Winning Percentage
  • OOWP = Opponents’ Opponents’ Winning Percentage

While the calculation may seem complex, RPI rankings are readily available online and are often updated hourly on various sports websites.

Interpreting RPI

The RPI helps provide a more comprehensive picture of a team’s performance beyond just their win-loss record. By emphasizing not only a team’s own winning percentage but also the strength of their schedule (as measured by their opponents’ records), the RPI can help identify which teams have truly earned their victories.

For example, a team with a slightly worse record that has played a tougher schedule may have a higher RPI than a team with more wins against weaker competition. This is especially important to consider when conference play begins and teams start facing more evenly-matched opponents.

RPI Rank

A team’s RPI can also be compared to all other Division 1 teams to produce an RPI Rank.

This rank indicates how a team stacks up against the entire field - a #1 RPI Rank means that the team has the best RPI in the nation, while a #100 RPI Rank would indicate a team is around the middle of the pack.

The RPI Rank is often used as a quick reference to gauge a team’s overall performance and is a key factor considered by the NCAA Tournament selection committee when determining at-large bids and seeding.

Limitations of RPI

While the RPI provides a useful snapshot of a team’s performance, it does have some limitations. One key factor it does not account for is the margin of victory - a team that consistently wins close games will have the same RPI as a team that dominates their opponents, all else being equal.

Additionally, because the RPI is based on winning percentage, it can sometimes overvalue teams that play weaker non-conference schedules before facing tougher competition in league play.

Despite these drawbacks, the RPI remains a central part of the college basketball landscape, particularly when it comes to postseason tournament selection.

While other metrics like the NET (NCAA Evaluation Tool) have been introduced in recent years, the RPI is still widely used and referenced by coaches, analysts, and fans alike.