I've been confused about how the quarterback rating was calculated for some time, but I just now found out how it's done, thanks to FARK. Checking out the official NFL site for an explanation of the quarterback rating has made things clearer, although I'm still dumbfounded as to why they arbitrarily decided that 158.3 was a perfect rating. Or rather, I'm confused as to why they used a seemingly arbitrary maximum limit (2.375) for each of four categories (percentage of completions, average yards per attempt, percentage of touchdown passes, and percentage of interceptions). The QB rating is calculated by adding calculations for all four of those categories (explained in more detail at the NFL page), dividing by six, and multiplying by 100. Therefore, a perfect QB rating is [(2.375 * 4) / 6] * 100 = 158.3. Peyton Manning managed a perfect rating two weeks ago in his rout of the Broncos in the AFC Wild Card game, which planted the seed in my mind that I need to figure this out. Finally...