RPI Calculation Steps

September 27, 2019 Baseball Blog Updates

RPI calculation example using 2018 Ashland Blazer football regular season, which is subject to revision given revisions approved for any RPI parameter. This long-published example of the calculations on the KHSAA website at https://ly.khsaa.org/uynq.

RPI Background (all sports)

• RPI stands for Ratings Percentage Index.
• RPI is used for district tiebreaking and football third, fourth and fifth-round bracketing, as well as a means to increase publicity, interest and promotion of interscholastic athletics.
• RPI is also used as a tiebreaking/contest-result mechanism to decide seeded district games that are not played by the deadline.
• The KHSAA is uniquely positioned to be the sole and authenticated source of RPI data due to the maintenance of required score reporting and scoreboard data for baseball, basketball, field hockey, football, soccer, softball and volleyball for more than two decades.
• RPI rankings are updated on an hourly basis but are not calculated for teams with missing scores from previous or multiple contests.
• The RPI formula is modeled after, but not identical to, similar measurement tools (e.g., NCAA, NAIA, etc.).
• RPI measures a team’s strength relative to other teams, based largely on the strength of its schedule (margin of victory is not a factor).
• RPI is calculated from the team’s winning percentage (WP), the opponents’ winning percentage (OWP) and the opponents’ opponents’ winning percentage (OOWP).
• RPI is calculated from the team’s winning percentage (WP), the opponents’ winning percentage (OWP) and the opponents’ opponents’ winning percentage (OOWP).
• These three components are combined to produce the RPI using the following formula: RPI = (WP * WPVAL) + (OWP * OWPVAL) + (OOWP * OOWPVAL).
  • WPVAL shall be .35 (35%).
  • OWPVAL shall be .35 (35%).
  • OOWPVAL shall be .30 (30%).
• An RPI of 0 is likely not possible in any scenario. From a mathematical perspective, a team would have to be winless, each of their opponents winless, and each of their opponents’ opponents winless.

Basic RPI Calculations (Not including football)

• In all of the calculations for all sports except football, the following values are assigned to game results when calculating WP throughout the compilation:
  • A win is assigned a value of 1.0 as a basis for comparison.
  • A tie is assigned a value of 0.5.
  • A loss is assigned a 0.0 value.
• Non-KHSAA Factor (all other than football)
  • For this example referenced below, games against out-of-state teams are automatically assigned a fixed value of .50 for the winning percentage in the final calculation for all sports except football.
  • Thousands of results throughout the country in a variety of states that have used the RPI reveal that in the end, the relatively few games played against out-of-state teams over the years average out and comparisons involving actual schedule results vary minimally statistically from that a .50 result used in most states, but the KHSAA has used its own historical data to help assign a different factor for non-KHSAA opponents.
  • Beginning with the 2023-2024 season, the out-of-state (now referred to as non-KHSAA) factor will be set on a two-year basis for all sports other than football, correlated to the out-of-state winning percentage of KHSAA schools against out-of-state opponents. For 2023-2024, this factor will be .53 in all sports except football.
  • The .53 non-member factor was selected as a representative average value of member schools’ winning percentages with respect to non-member opponents across all sports using past results since the initial usage of RPI by the KHSAA.
  • This same value of .53 is also assigned to any in-state approved home school team as they are non-member schools without score reporting requirements.
  • This non-KHSAA value is also assigned in the WP calculation for an in-state home school competing against a member school.
• WP is the Winning Percentage of the team being considered.
  • The WP is computed by taking the number of wins and dividing by the number of games played. A 15-4 team would have a WP of 15 wins/19 games = 0.789.
  • Ties are counted as 1/2 of a win (a win value of .5), so a 15-3-1 team would have a WP of (15+.5)/19 = 0.816.
• OWP is the Opponent’s Winning Percentage which is the average of the WP of each of the opponents the team has played.
  • The WP for each of the opponents is calculated like the WP for the team with one big exception: none of the games with the team whose RPI is being determined are included when calculating the WP of the opponents.
  • As an example, consider an opponent that has a 9-1 record and that the only loss is against the team under consideration. Excluding that game, the opponent has a 1.000 record, which is what will be used in computing its relative schedule strength.
  • In the example regarding Ashland Blazer, which illustrates that when calculating the OWP, each of Ashland Blazer’s opponents’ winning percentages is calculated. But in each one of those, the game against Ashland Blazer is excluded. A win over Ashland Blazer does not help the WP value used in the calculation for Ashland Blazer’s OWP, nor does a loss hurt that WP. That game is not included in the calculation.
• OOWP is the Opponent’s Opponents’ Winning Percentage and is calculated by looking at each opponent and calculating their OWP, similarly excluding the games between the opponent and their opponents. The OOWP is the average of the OWP for each opponent.
  • The exclusion of the considered team extends to the calculation of the OOWP as well.
  • In the example regarding Ashland Blazer, each of their opponents now becomes the compared team. So when performing the calculation for Raceland, the WP for each of their opponents is calculated. Therefore when performing the calculation, the WP for Greenup County must be computed. The game between Raceland and Greenup County will not be used in the calculation for Raceland’s WP. However, the game between Ashland Blazer and Greenup will be calculated within the OOWP.

Basic RPI Calculations (Football)

• In football, the following values are assigned to game results when calculating WP throughout the compilation:
  • A win is assigned a value of 1.0 as a basis for comparison.
  • A tie is assigned a value of 0.5.
  • A loss is assigned a 0.0 value.
  • In addition, football has a class factor added to the formula and special situations for when that is and it not applied.
• Non_KHSAA Factor (football)
  • For football only, the non-KHSAA value is set to a fixed value based on pre-COVID competition results.
  • That value is .51060 and is reviewed following each season.
• Due to the limited number of contests for football compared to the other sports and the fact that football is divided into classes, and as the KHSAA office maintains the official district standings, there are additional clarifications and operations in football that are not necessary for other sports, as follows:
  • A team is eligible to play 10 contests during the 11-week season;
  • All games played, including forfeits, count as normal with RPI;
  • A seeded district or contracted game unable to be played without forfeit attribution will be decided by comparative RPI following the last regular-season game;
  • A class factor is applied to the football RPI calculations through the WP calculation;
    • Beginning with the 2023 season, the first two contests of the year played against a team in a smaller class will not have the opponent’s class factor applied within the OWP and thus, OOWP calculation but will instead be treated as both teams being in the same class.
    • However, all contests played against opponents in a higher class will have the class factor applied to the more highly classified opponent.
    • With this new provision for two play-downs, when calculating OWP and OOWP in football, there are no “Playing Down” exemptions.
• Winning Percentage Calculation for Football
  • Football is a special case, and enhancements are made to the winning percentages.
  • These percentages are adjusted by multiplying by a game value based on the class of the opponent in football, primarily due to the limited number of opportunities to play contests and to compensate for schools playing in a different class than they might otherwise be placed by enrollment.
  • It should also be noted that by using class weights, as is done in football, it is possible to get WP greater than 1.000 but less likely in the higher class listings due to less opportunities for playing up.
  • It is possible to get OWP, OOWP, and even RPI that is greater than 1.000 due to class weights.
  • Kentucky has six football classes, Classes 1-6A, which generally reflects the enrollment of the school.
  • The WP calculations are adjusted to give more weight to a game when a school “Plays Up” by playing a higher class and give less weight to games when a school “Plays Down” by playing a lower class (after exhausting two allowed “Playing Down” exemptions beginning in 2023-24).
  • This weight is used to adjust the value of a win depending on the team’s class and the opponent’s class.
    • If the game is a win for the team, the Winning Percentage of the game is the class weight (the Winning Value in the example) for the opponent divided by the class weight of the team (the Game Value in the example). This gives the Winning Percentage for that game.
    • Consider the game between Ashland Blazer and Harlan County in the published example. Ashland Blazer (a Class 4A team) won against Harlan County (a Class 5A team). So, the Winning Percentage for this game is 2.313/2.011 = 1.15017. On the other hand, consider the game between Ashland Blazer and Russell (a Class 3A team). Ashland won this game, too. So, the Winning Percentage of this game is 1.749/2.011 = 0.86972 (assuming this game occurred after Ashland Blazer had exhausted its two allowed “Playing Down” exemptions).
  • This produces the desired outcome as Ashland Blazer “played up” in class when it played Harlan County, so the Winning Percentage of that game is greater than the win against Russell because Ashland Blazer “played down” in class.