Math on New 2 Point Conversion & Extra Point Rule

The NFL agreed, for the first two preseason games, to place the extra point at the 20 yard line instead of where it previously sat at the 2 yard line.  While 2 point conversions are still going to occur from the 2 yard line, teams will be faced with the decision:

  • Do I kick a 38 yard field goal or
  • Do I attempt to convert a single play from the 2 yard line to reach the end zone

Fortunately, we have plenty of data to weigh in on league averages and thus, “average” decision making.  However, teams success rates vary widely as you will see below, so I would assume each team would be running their own numbers to determine which strategy benefits them the most.  And of course, everything also must be run on their opponent, as certain teams are more easily scored on than others.  That said…

Since 2002, there have been 402 field goal attempts from exactly 38 yards, with 86.6% of them being kicked successfully.  So theoretically the average team with the average kicker will gain an average of 0.866 points per attempt on these new extra point kicks.

Meanwhile, for all 2 point conversion attempts since 2002, there have been 728 league wide with 49.9% of them being converted successfully.  Theoretically the average team with the average conversion offense vs an average conversion defense will gain an average of 0.998 points per attempt on 2 point conversions (49.9% x 2 points).

As you can see, it certainly makes more sense based on league averages to go for the 2 point conversion (0.998 expected points) rather than the extended extra point (0.866 expected points).

The break even point would be a team who, vs a particular defense, is able to convert just 43.3% of its 2 point conversions (6.6% below league average).  Such a team would gain exactly 0.866 expected points on two point conversions (0.433 x 2 points), equivalent to the league average for the new extended extra point.

Again, all of this assumes EVERYTHING is average (kicker, 2 point conversion offense, 2 point conversion defense) and as we know, very few games will feature precisely average kickers, average 2 point conversion offenses and 2 point conversion defenses.  And my sample size goes back to division realignment in 2002, and teams will want to use more reflective projections of their current team despite the inherent risk of capturing too low a sample size.

Of course, game situation is a huge factor as well, and in late and close games, tied or trailing by 1 point, the risk of failure on the 2 point attempt (50.1%) far outweighs the extra expected points, especially when the risk of failure for the extra point is only 13.4%.  Teams will also use a similar thought process to place the game on key numbers of 3, 7 and (now) 8.

This is all conjecture at this point because we don’t know if the NFL will ultimately play regular season games by these rules, but assuming it makes the first 2 weeks of the preseason more interesting, I imagine they will approve it for 2015.

Below is a summary of the 2 point conversion success rates since 2002 for offense and defense by team.

Click to enlarge