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Understanding the Slate Index

The Slate Index is a college football rating system designed to predict a team’s performance against an average FBS team on a neutral field. The core metric, Score Margin (SM), indicates the expected point difference in such a matchup. For example, if LSU has a SM of +15.0, they are projected to beat the average FBS team (SM: 0) by 15 points.

Rating Metrics:

  • Points For Rating (OFF): The estimated points the team would score against an average FBS defense. The 2025 Preseason most average FBS defense is Pittsburgh (PA Rating of 28.1)
  • Points Allowed Rating (DEF): The estimated amount of points an average FBS offense would score on the team. The 2025 Preseason ratings suggest that Cincinnati has the most average offense (PF Rating of 28.5).
  • Special Team Rating (ST): measures how much a team relies on its ST unit to score points not the talent of the ST unit. Using historical games, it weights longer and more difficult field goals—and stalled drives that force long kicks—more heavily. 
  • Strength of Schedule (SoS): Average SM of a team’s opponents. For example, if Georgia’s SOS is +8, their average opponent would beat the average FBS team by 8 points

Game Score Calculation

To calculate a team’s expected points, add the team’s PF and their opponent’s PA, then subtract 28.3. If the game is not neutral, adjust for home-field advantage by adding 1.27 (half of the 2.54 home-field advantage) to the home team’s expected points and subtracting 1.22 from the away team’s expected points. This method assumes home-field advantage equally impacts both offense and defense.

Formulas:

  • Home / Away Site:
    • Home Team Points: Home OFF Rating + Home ST Rating + Away DEF Rating – 28.3 + 1.27
    • Away Team Points: Away OFF Rating + Away ST Rating + Home DEF Rating – 28.3 – 1.27
  • Neutral Site:
    • Team 1 Score: Team 1 OFF Rating + Home ST Rating + Team 2 DEF Rating – 28.3
    • Team 2 Score: Team 2 OFF Rating + Away ST Rating + Team 1 DEF Rating – 28.3

Example:

Texas (Home) vs. LSU (Away)

  • Texas: PF = 30, ST = .6,  PA = 22
  • LSU: PF = 38, ST = .8, PA = 29

Calculations:

  • Texas Points: 30 + 0.6 + 29 – 28.3 + 1.27 = 32.03
  • LSU Points: 38 + 0.8 + 22 – 28.3 – 1.27 = 30.51

Limitations of the Slate Index

Home Field Advantage: The Slate Index assumes a standard Home Field Advantage of 2.54 points for every non-neutral site game. This means the home team benefits by 1.22 points for playing at their own stadium, while the away team is disadvantaged by 1.22 points. However, this assumption doesn’t account for the varying degrees of home field advantages across different stadiums. For example, a night game in Death Valley for LSU is treated the same as a noon game between two smaller FBS programs.

FBS vs. FBS Matchups: Only games between FBS teams are included in the Slate Index ratings. This means a team’s performance against FCS teams, whether good or bad, does not affect their ratings. This decision was made to maintain the model’s relativity among the 138 FBS teams and provide a true scale of team strength. Including FCS matchups could distort team metrics due to significant differences in overall strength.

“Most Deserving”: The primary goal of the Slate Index is to assess the value of each team relative to the rest of the league. This model does not account for which team may be “more deserving” of a higher rating. The ratings are based on a combination of scoreboard dominance and strength of schedule. 

2020 Ratings: A basic principle of the rating system is that more games played provide the system with more data to accurately assess a football team’s strength. Additionally, the more interconnected the teams’ schedules are, the easier it is to statistically compare and rate them within the league. 

Acknowledgment

All data has been provided by College Football Data. A special thank you to them for allowing open source use for data analytic projects like this. A special thank you to Football Study Hall for their in depth study on Garbage Time in College Football.

Ranking Principles

The principles for Score Margin and Yard Margin rankings are based on concepts from the ELO and Massey method. For more detailed sports ratings, please visit Massey Ratings. More information on the ELO method can be found here: ELO Method 

Understanding the Slate Index (2019 – 2023)

The Slate Index is a comprehensive rating system for FBS college football teams, designed to evaluate their overall performance and provide insights into the strength of their offense and defense. The system aims to determine the relative strength of each team based on key metrics and principles.

Principles of Evaluation

The Slate Index is built on three football principles that Slate Fluker defines as priorities when determining a team’s relative strength:

  1. What teams did you beat? (Record Strength)
  2. How badly did you beat them? (Scoring Margin)
  3. How dominant was your performance? (Yard Margin)

Overall Rating (OVR)

The OVR rating indicates how many FBS teams a specific team is rated above. For example, if Michigan has an OVR rating of 96.5%, it means Michigan is better than 96.5% of all FBS teams. The OVR rating is derived from three key statistics:

  1. Record Strength (RS): Evaluates a team’s wins and losses, considering the strength of the opponents each team defeated.
  2. Scoring Margin (SM): Calculates the expected margin of victory or defeat against an average opponent on a neutral field. Hypothetical game margins are calculated using specific formulas for regular games and neutral site games. For example, if Georgia (SM rating of 28.4) hosts Tennessee (SM rating of 15.5), Georgia would be expected to win by 15.33 points.
    • Formula: 2.43 (Home Field Advantage) + (28.4 – 15.5).
  3. Yard Margin (YM): Measures the yardage difference a team is expected to have against an average opponent on a neutral field. This metric reflects how effectively a team drives the field and prevents their opponent from doing the same, independent of the final score.

Additional Considerations

  • Metric Ratings: A rating of 0 represents an average team, above 0 indicates a better-than-average team, and below 0 signifies a below-average team.
  • Adjustments: All statistics are adjusted for opponent strength, excluding garbage time while including home-field advantage to better understand each team’s overall strength. Home-field advantage (HFA) is determined at an FBS average of 2.43 points.
  • Exclusions: Games against FCS teams are excluded to maintain accuracy. Important games, such as conference championships and College Football Playoff matchups, are weighted more heavily, significantly influencing a team’s strength.

This structured approach ensures that the Slate Index provides a clear and accurate assessment of each FBS team’s performance, reflecting their true competitive strength in college football.

Offense Rating (OFF)

The Offense Rating (OFF) is a statistical measure indicating how well a team’s offense performs relative to all FBS teams. The percentage represents the number of FBS teams the offense outperformed. For example, if Alabama has an offense rating of 94%, it means their offense is better than 94% of all FBS teams.

  • Expected Points For (EPF): Estimates the number of points a team would score against an average opponent on a neutral field.
  • Expected Yards For (EYF): Estimates the yards a team would generate against an average opponent on a neutral field.

Defense Rating (DEF)

The Defense Rating (DEF) is a statistical measure indicating how well a team’s defense performs relative to all FBS teams. The percentage represents the number of FBS teams the defense outperformed. For example, if Texas has a defensive rating of 92%, it means their defense is better than 92% of all FBS teams.

  • Expected Points Allowed (EPA): Predicts the number of points an average opponent on a neutral field would score against the team.
  • Expected Yards Allowed (EYA): Estimates the yards an average opponent on a neutral field would gain against the team.

2020 

However, in 2020, the number of games played varied widely, leading to some team ratings being overstated or understated. For example, Arizona played only five games and lost all of them. If they had a full schedule, their rating might have been higher. Many teams only played conference matchups, making it difficult to compare teams across different conferences. This effect is evident with Buffalo (Rank: 6) and Ball State (Rank: 7), who dominated their in-conference matchups. Ball State’s single loss to Miami (OH) significantly boosted Miami’s rating despite the Redhawks only playing three games. Due to these factors, the 2020 ratings were less accurate than in other years, largely because of the disruptions caused by Covid.

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