Every quarterback page on this site shows two numbers near the top of the passing table: passer rating and EPA per dropback. They often agree. When they don't, the gap usually tells you something about how a quarterback plays.
What passer rating measures
Passer rating is the NFL's official passing formula, adopted in 1973. It takes four rates per attempt: completion percentage, yards per attempt, touchdown rate and interception rate. Each piece is scaled, capped so one great number can't carry the rest, and the four are averaged into a single score where 158.3 is perfect. Because the inputs are in every box score back to the 1930s, passer rating is easy to compare across eras and easy to check.
It also has blind spots. Sacks don't count at all, so a quarterback who holds the ball and takes a 9-yard loss is untouched while one who throws it away gets an incompletion. Scrambles and designed runs don't count. And every attempt is treated the same: a 6-yard completion on 3rd and 5 is identical to a 6-yard completion on 3rd and 10, even though one keeps the drive alive and the other leads to a punt.
What EPA measures
Expected points is a standard idea in football analytics: from any down, distance and field position, how many points does an average offense go on to score? A 1st and 10 at your own 25 is worth a bit under one point. A 1st and goal at the 2 is worth about five. Expected points added (EPA) is the change from the start of a play to the end of it.
That makes EPA sensitive to everything passer rating misses. The 6-yard throw on 3rd and 5 earns positive EPA because it moves the chains; the same throw on 3rd and 10 earns negative EPA because a punt is coming. A sack costs EPA, a scramble for a first down gains it, and an interception near the other team's goal line costs far less than one thrown from your own 20.
We use nflverse's quarterback EPA, which does not charge the passer for a receiver's fumble after the catch, and we divide by dropbacks: pass attempts, sacks and scrambles. Spikes and kneel-downs are left out because they are clock plays, not decisions.
Why we rank by EPA per dropback
EPA per dropback gives credit for the throw that matters in the moment, counts sacks against the passer, and credits the scrambles that save a drive. It also works the same way in college and the NFL, which matters for a site that keeps a player's whole career on one page. That is why it leads our quarterback rankings.
What passer rating still gets right
Passer rating is transparent: you can calculate it with a pencil. It is the number broadcasters quote and the one most readers know, and the parts it measures (completing passes, gaining yards, finding the end zone, avoiding interceptions) are the core of the job. We show it beside EPA so the two can check each other.
How to read them together
- High rating, modest EPA: often a quarterback who completes safe, short throws but takes sacks or misses on third down.
- Modest rating, high EPA: often a passer who converts third downs, scrambles well or avoids sacks, even with a lower completion rate.
- Both high: a very good season. Check ACE next to see how much of it came from accuracy on hard throws.