 Passer rating attempts to sum up how good a quarterback is with one number. It can be used for individual games, but more importantly, the NFL uses it to determine its passing leader each season, as opposed to yards passing or completion percentage as they've used in the past. Passer rating cares about four numbers, completion percentage, yards per attempt, your touchdown per attempt percentage, and interceptions per attempt percentage. In other words, complete the passes that you attempt. The more yards per pass the better, TD passes are good and interceptions are bad. Seems reasonable. Each of these four figures are treated as equally important, so you can't slack off in any category. Even if you have a great day with lots of yardage and touchdown passes, throwing a few interceptions can still tank your passer rating. One of the confusing aspects of the passer rating, and probably one of the main reasons for any confusion around the stat, is that it runs on a scale from zero to 158.3, which isn't necessarily intuitive. If we look at passer ratings from over the years, it's clear that the game has become much more passing oriented. Over the last five years, the average passer rating for a season is about 89. This means that the average quarterback is completing two out of every three passes for about seven yards per attempt. He's throwing one touchdown for every 20 attempts and one interception for every 50. Keep in mind that other than completion percentage, passer rating cares about passes thrown, not passes completed. So in most games nowadays, a quarterback will have a passer rating between 60 and 120. A perfect game in terms of passer rating means completing almost 80% of passes with 12 and a half yards per attempt, at least one touchdown pass every eight attempts and no interceptions. Since 1960, there have been 52 quarterbacks to have a perfect passer rated game with Peyton Manning and Big Ben leading the way with four each. And while it's obviously indicative of a good game for a quarterback, it's not necessarily a guarantee. Four of these quarterbacks with perfect scores actually lost their game. Over a whole season, Aaron Rodgers has the high mark with 122 and a half in 2011. Sammy Baugh in the 1940s and Steve Young in the 90s, both led the league six different seasons with young ones leading at four years in a row from 1991 to 94. On the other end of the spectrum, anything less than a 30% completion percentage, three yards per attempt, one pick for every 10 attempts and no touchdowns will result in a passer rating of zero. Again, each category is separate so no matter how many interceptions you throw, if you can manage at least one touchdown pass, you'll avoid a zero. So getting a zero means you've struggled in basically every aspect. Zero rated games have happened 66 times since the merger. Two of those came on a sad day in 1973 when Bob Lee of the Atlanta Falcons, Gary Keith Lee of the St. Louis Cardinals both picked up zero ratings in the same game. Terry Bradshaw has the record with three zero rated games, although he is one of 12 quarterbacks to have both a zero and a perfect rated game under his belt. Passer rating has both proponents and its critics. Writing for Sports Illustrated, Kerry Bryan wrote that regardless of the era, successful teams always seem to rank high in passer rating differential. That is, your team's passer rating minus your opponents. Quote, teams that had a higher passer rating went 203 and 53 in 2010. Don't tell us that a stat that identifies the winner all by itself, 80% of the time, isn't one of the most important stats in sports. Then again, it also has its detractors. ESPN took it upon themselves to create a new stat called Total Quarterback Rating, or QBR. This stat is proprietary, so we don't really know the actual formula. Although unlike passer rating, it does incorporate rushing, penalties, and sacks. And in some cases, yours after the catch may not be included in the formula either. Speaking of formulas, before we wrap up, the formula for passer rating is as follows, where we have our four parts, A, B, C, and D. Each of these, when entered into the final formula, can only have a value between zero and 2.375. So regardless of whether you complete 90 or 100% of your passes, the A portion will be over 2.375. But when we enter it into the formula, we use 2.375 rather than the actual figure. And on the flip side, any figure that ends up as a negative number is entered as zero. Plug everything in, and it's pretty simple math from there on out.