How to Calculate Football Passer Ratings

The term "passer rating" can refer either to an NFL quarterback's rating, or a NCAA quarterback's passer efficiency. The NFL and NCAA use completely different calculations to determine the rating. In addition, the ratings have different meanings. The NFL's rating ranges from 0.00 to 158.3, with a rating of 100 considered very good. The NCAA rating ranges from (negative) 200 to 1,261.6, with a rating of 100 considered average. Both formulas used to calculate passer ratings are fairly basic. With a calculator and the necessary statistics you can determine a passer's rating yourself.

Things You'll Need

• Statistics
• Calculator

Instructions

NFL Formula

1. Gather the statistics needed to calculate the passer's rating. You'll need the quarterback's completion percentage, average yards per attempt, touchdown pass percentage and interception percentage.

   David Garrard's (Jacksonville Jaguars) statistics from the 2007 season are used for the sample.

   Completion percentage: 64 percent
   Yards per attempt: 7.7
   Touchdown percentage: 5.5 percent
   Interception percentage: 0.9 percent

2. Subtract 30 percentage points from the completion percentage. Multiply the result by 0.05.

   Sample: 64 - 30 = 34 × 0.05 = 1.7

3. Subtract three yards from the average yards per attempt. Multiply the result by 0.25.

   Sample: 7.7 - 3 = 4.7 × 0.25 = 1.175

4. Multiply the touchdown pass percentage by 0.2.

   Sample: 5.5 × 0.2 = 1.1

5. Multiply the interception percentage by 0.25, and then subtract the result from 2.375.

   Sample: 0.9 × 0.25 = 0.225; 2.375 - 0.225 = 2.15

6. Add up the total points produced by the calculations. Divide the result by six, and then multiply it by 100.

   Sample: 1.7+1.175+1.1+2.15 = 6.125

   6.125 ÷ 6 = 1.0208

   1.0208 × 100 = 102.08

   For the 2007 season, David Garrard's passer rating was 102.08.

NCAA Formula

1. Gather the statistics needed. The same statistics used by the NFL are used by the NCAA. This includes the completion percentage, yards per attempt, touchdown percentage and interception percentage.

   The sample used is Joe Flacco's 2007 NCAA season statistics.

   Completion percentage: 63.5
   Yards per attempt: 8.18
   Touchdown percentage: 4.41 percent
   Interception percentage: 0.96 percent

2. Multiply the yards per attempt by 8.4.

   Sample: 8.18 × 8.4 = 68.71

3. Multiply the touchdown percentage by 3.3.

   Sample: 4.41 × 3.3 = 14.55

4. Multiply the interception percentage by 2.

   Sample: 0.96 × 2 = 1.92

5. Add the sums of step two and three to the completion percentage.

   Sample: 68.71 + 14.55 + 63.53 = 146.79

6. Subtract that total by the number derived from the interception percentage.

   Sample: 146.79 - 1.92 = 144.87

   Joe Flacco's NCAA passer rating was 144.87 during the 2007 college football season.

Tips & Warnings

• All the statistics required are quite easy to find for professional and college players. However, you may not have access to statistics like "yards per attempt" or "touchdown percentage." Here's how to calculate them:

• Completion percentage: Completions divided by attempts times 100.

• Yards per attempt: Yards divided by the number of attempts

• Touchdown percentage: Touchdowns divided by the number of attempts times 100.

• Interception percentage: Interceptions divided by the number of attempts times 100.

• If the interception percentage is higher than 9.5 percent (very rare), the NFL rating system does not award any "points" for this statistic. If this is the case, simply use "0" instead of following the interception percentage formula.

References

• NFL.com: QB Ratings
• NFL.com: David Garrard
• NCAA.org: Statistician's Handbook (PDF)

Resources

• Pro Football Reference