The Perfect Passer Rating

NFL Passer Rating

In 1973, the NFL introduced its official measurement for quarterback performances -- the Passer Rating. The measurement is based on 4 equally weighted components (completion percentage, yards per attempt, touchdowns, and interceptions) that are averaged together and then scaled up to create a more digestible number. To avoid any one component from skewing the metric, the metric's creator, Don Smith, constrained individual component values between 0 and 2.375 (before scaling). Since each component has a maximum value, that means that the entire metric has a mathematical maximum too--158.3 to be exact.

From a statistical standpoint, a rating of 158.3 holds no special meaning. It is an arbitrary byproduct created by the metric's methodology. But from a fan's perspective, a rating of 158.3 is perfect. The pinnacle of quarterbacking. A perfect passer rating. As such, we have a tendency to ascribe special meaning to games in which it occurs.

Let's break down exactly how a perfect rating is achieved, how many times it's been done, and how it compares to other metrics like QBR and EPA per play.

What's required to achieve a perfect rating?

Passer rating is an efficiency statistic with each component measured on a per attempt basis. As a result, the number of completions, passing yards and touchdown passes required for a perfect passer rating change depending on the number of pass attempts. However, a minimum "rate" for each component can be calculated.

The minimum requirements for a perfect passer rating are:

• 77.5% Completion Percentage

• 12.5 Yards per attempt

• 11.9% Touchdown Rate

• 0% Interception Rate (ie zero interceptions)

If a quarterback fails to achieve any one of the above stats, they will not receive a perfect passer rating, which you can explore using a passer rating calculator.

How Many QBs have achieved a perfect rating?

As of this writing, a perfect passer rating has been achieved 61 times since it was introduced to the NFL in 1973. That means that a perfect passer rating is achieved every 201 games, which translates to just 0.25% of starts.

Perhaps must surprising is the list of QBs who have achieved a perfect passer rating. It includes many of the greats like Tom Brady, Peyton Manning, Drew Brees, Kurt Warner, Ben Roethlisberger, and Aaron Rodgers, but also a long list of the not so good. For instance, Alex Smith, Jared Goff, and Marcus Mariota of also reached a mark of 158.3 at least once.

To really show how odd the notion of a perfect passer rating can be, consider that ten QBs who have achieved a perfect rating have also had a game in which they recorded a passer rating of 0, which is the lowest possible passer rating.

Passer Rating, QBR, and Expected Points Added (EPA)

In the 50 years since passer ratings were introduced to the NFL, advancements in analytics have given us better metrics for measuring quarterback performances, most notably, QBR and Expected Points Added (EPA).

As shown in previous analysis on QB metrics, passer rating holds up better to these new stats than most might think, but it can struggle to capture the contextual nuance that goes into quarterback performances. The highest passer rating does not always equal the highest EPA per attempt or QBR.

Sometimes, the stats align. Take for example Lamar Jackson's staggering Week 1 performance in 2019 against the Dolphins in which he completed 23 of 26 passes for 379 yards, 6 touchdown passes, and 0 interceptions. In addition to a perfect passer rating, this performance netted a QBR of 99.5 (out of 100) and an EPA per play of 1.4, which is about as high as you'll see EPA get.

By comparison, take Kirk Cousins' perfect passer rating game against the Saints in 2015. In this game, Cousins completed 20 of 25 pass attempts for 324 yards, 4 touchdown passes, and 0 interceptions. While this performance looks comparable to Jackson's (or any other perfect game), it yielded a QBR of only 56 and an EPA per play of 0.61.

For context, a QBR of 56 is considered slightly above average. The lowest ever passer rating achieved by a player who also received a 56 QBR was Sean Hill against the Patriots in 2010 when he threw for 1 touchdown, 2 interceptions, 285 yards, and completed 27 of his 46 pass attempts. By complete coincidence, his opponent in that game, Tom Brady, finished with a perfect passer rating of 158.3.

It's a similar story, though maybe a bit better, for EPA. The lowest EPA per play in a game where the QB achieved a perfect passer rating is 0.53 by Ryan Tannehill against the Texans in 2015. The lowest QB rating by a player who achieved an EPA per play of 0.53 or better is 96.9, achieved by Peyton Manning against the Packers, which also occurred in 2015.

What does it all mean?

At the end of the day, all quarterback metrics are just tools for comparing quarterbacks. We can have perfect games by one metric that are just average by another. While the notion of measuring perfect games is fun and interesting, it's ultimately a fleeting exercise. 

When metrics can disagree by such a wide margin, as shown by looking at single game oddities for passer rating, QBR, and EPA, it means that they are each imperfect in some way. If these separate calculations could all measure NFL quarterbacks perfectly (for lack of a better word), they'd agree on what perfect looked like.

So take perfect ratings with a grain of salt. It's just one measurement.