Championship Rematch Odds

Now that the conferences are all trending towards divisionless formats, what are the odds of seeing rematches in the conference championship games?

Each conference has or had different odds based on number of teams and number of games.  Let's list all of the possible configurations from the least likely to provide a rematch to most likely.

14 teams (2 divisions of 7) / 8 game schedule
-used by the ACC from 2013-2022 and the SEC through 2023

Each team would play 6 teams in their division, plus 2 from the opposite.

Out of 7 possible opponents, any team would have already played 2.

Rematch chance:  2/7 = 28.5%

Of the 9 years that the ACC used this format (2013-2022 except for 2020), there was never a rematch in the title game.

14 teams (2 divisions of 7) / 9 game schedule
-used by the B1G through 2023

Each team plays 6 divisional games, plus 3 from the other side.

Rematch chance:  3/7 = 42.85%

12 teams (2 divisions of 6) / 8 game schedule
-used by the ACC and SEC prior to the last round of expansion

Each team would play the 5 teams in their division, plus 3 from the opposite division.

Any team from one division could face 1 of 6 teams from the opposite side, but already played three.

3/6 = 50% chance of a rematch.

Interestingly enough, of the 8 years that the ACC used this format, exactly half of their championship games were rematches.  Three of the four rematches involved teams who were permanent crossover rivals (VT/BC in 2007 and 2008, and GT/Clemson in 2009).

18 teams (no divisions) / 9 game schedule
-B1G starting in 2024

Out of 17 possible opponents, a team would have already played 9.

Rematch chance:  9/17 = 52.94%

16 teams (no divisions) / 8 game schedule
-SEC starting in 2024

Out of 15 possible opponents, a team would have already played 8.

Rematch chance:  8/15 = 53.3%

16 teams (no divisions) / 9 game schedule
-Big 12 starting in 2024

Out of 15 possible opponents, a team would have already played 9.

Rematch chance:  9/15 = 60%

14 teams (no divisions) / 8 game schedule
-current ACC format

Any team could play any of the other 13 teams in the conference, having already played 8 of them in the regular season.  

Rematch chance:  8/13 = 61.5%

14 teams (no divisions) / 9 game schedule
-used by the Big 12 in 2023

Out of 15 possible opponents, a team would have already played 9.

Rematch chance:  9/15 = 64.25%

12 teams (2 divisions of 6) / 9 game schedule
-used by the Pac-12 through 2021

Each team would play 5 teams from their division, plus 4 from the opposite division.

Rematch chance:  4/6 = 66%

12 teams (no divisions) / 9 game schedule
-used by the Pac-12 in 2022-2023

Out of 11 possible opponents, a team would have already played 9.

Rematch chance:  9/11 = 81.8%

10 teams (no divisions) / 9 game schedule
-used by the Big 12 through 2022

This is a round robin format, guaranteed to create a rematch.

Rematch chance:  9/9 = 100%