What it is

Passer rating is a formula that rates a quarterback using completions, yards, touchdowns and interceptions per attempt. A perfect score is 158.3.

In a game

Higher is better. It was created in the 1970s as a way to compare quarterbacks across eras.

More detail

The formula has four parts, each capped at the same maximum. Critics say it ignores sacks, rushing and the situation, so newer stats have been created. Still, it is widely quoted.