NFL's Passer Rating

In the early 1970s, a special study committee headed by the late Don Smith of the Pro Football Hall of Fame; Seymour Siwoff of Elias Sports Bureau (the official NFL statisticians); and the late Don Weiss of the National Football League created the passer rating that is now in use in the NFL. 

Smith and Siwoff did the experimentation and statistical testing on the basis of performance standards extracted from the stats of all qualified pro football passers since 1960. The system was adopted by the NFL in 1973.

 QBs with 100 point seasons

Current Passer Rating System:
Source: 2010 National Football League Record & Fact Book

The NFL rates its passers for statistical purposes against a fixed performance standard based on statistical achievements of all qualified pro passers since 1960. The current system replaced one that rated passers in relation to their position in a total group based on various criteria. The current system, which was adopted in 1973, removes inequities that existed in the former method and, at the same time, provides a means of comparing passing performances from one season to the next.

It is important to remember that the system is used to rate passers, not quarterbacks. Statistics do not reflect leadership,
play-calling, and other intangible factors that go into making a successful professional quarterback.

Four categories are used as a basis for compiling a rating:
Percentage of completions per attempt
Average yards gained per attempt
Percentage of touchdown passes per attempt
Percentage of interceptions per attempt

The average standard is 1.000. The bottom is .000. To earn a 2.000 rating, a passer must perform at exceptional levels, i.e., 70 percent in completions, 10 percent in touchdowns, 1.5 percent in interceptions, and 11 yards average gain per pass attempt. The maximum a passer can receive in any category is 2.375.

For example, to gain a 2.375 in completion percentage, a passer would have to complete 77.5 percent of his passes. The NFL record is 70.55 by Ken Anderson (Cincinnati, 1982). To earn a 2.375 in percentage of touchdowns, a passer would have to achieve a percentage of 11.9. The record is 13.9 by Sid Luckman (Chicago, 1943). To gain 2.375 in percentage of interceptions, a passer would have to go the entire season without an interception. The 2.375 figure in average yards is 12.50, compared with the NFL record of 11.17 by Tommy O’Connell (Cleveland, 1957).

In order to make the rating more understandable, the point rating is then converted into a scale of 100, with 158.3 being the highest rating a passer can achieve. In cases where statistical performance has been superior, it is possible for a passer to surpass a 100 rating.

For example, take Peyton Manning’s record-setting season in 2004 when he completed 336 of 497 passes for 4,557 yards, 49 touchdowns, and 10 interceptions. The four calculations would be:
Percentage of Completions—336 of 497 is 67.60 percent. Subtract 30 from the completion percentage (37.60) and multiply the result by 0.05. The result is a point rating of 1.880. Note: If the result is less than zero (Comp. Pct. less than 30.0), award zero points. If the results are greater than 2.375 (Comp. Pct. greater than 77.5), award 2.375.
Average Yards Gained Per Attempt—4,557 yards divided by 497 attempts is 9.17. Subtract three yards from yards-perattempt (6.17) and multiply the result by 0.25. The result is 1.543. Note: If the result is less than zero (yards per attempt less than 3.0), award zero points. If the result is greater than 2.375 (yards per attempt greater than 12.5), award 2.375 points.
Percentage of Touchdown Passes—49 touchdowns in 497 attempts is 9.86 percent. Multiply the touchdown percentage by 0.2. The result is 1.972. Note: If the result is greater than 2.375 (touchdown percentage greater than 11.875), award 2.375.
Percentage of Interceptions—10 interceptions in 497 attempts is 2.01 percent. Multiply the interception percentage by
0.25 (0.503) and subtract the number from 2.375. The result is 1.872. Note: If the result is less than zero (interception percentage greater than 9.5), award zero points.

The sum of the four steps is (1.880 + 1.543 + 1.972 + 1.872) 7.267. The sum is then divided by six (1.211) and multiplied
by 100. In this case, the result is 121.1. This same formula can be used to determine a passer rating for any player who
attempts at least one pass.
 

Timeline of Methods Used by the NFL to Determine Passing Leaders

Since the NFL first started keeping official statistics in 1932, the following are the different ways in which the passing champions were determined.

1932-1937
Total yards passing
1938-1940
Percentage of completions
1941-1948
Inverse ranking system of the following categories: completions, percentage of completions, total yards, total TD passes, number of interceptions, and percentage of interceptions.
1949
The same formula used from 1941-148 except the number of interceptions was dropped from the equation.
1950-1959
Average yards gained per pass with a minimum of 100 attempts needed to qualify.
1960-1961
Inverse ranking system based on six categories: total completions, total yards, total TD passes, percentage of completions, percentage of interceptions, average gain per attempt with the principle established of at least 10 attempts per game to qualify.
1962-1971
Inverse ranking system based on four categories: Percentage of completions, total touchdown passes, percentage of interceptions, average gain per attempt.
1972
Same system used from 1962 to 1971 except that the percentage of touchdown passes was substituted for total touchdown passes.
1973-present
Rating system described above.