How does ESPN compute their total QBR?

I have no idea how it works, however I do know that it's extremely flawed, and pretty much a joke. Only the crew at espn try to convince themselves that it's actually valid. If you were to look up some of the horrific stats of QB's in games that ended up with a high QBR for those very same games, you would be shaking your head in disbelief. Passer rating is much more accurate. Me, I look at yards, touchdowns, interceptions; pretty basic. I will also look at passing attempts and completions.

According to ESPN, it "...took several thousand lines of code to implement" the QBR system. It's supposed to measure how "clutch" a quarterback is so Brady would have a lower rating because New England usually blows their opponents out.

The NFL " EXPERTS" at ESPN came up with it, I think it's mostly just their opinions

I don't think anyone really knows, which is why nobody else uses it or even acknowledges it.