I found this.
What is the formula for the NCAA QBR?
The NCAA formula is: [ { (8.4 * yards) + (330 * touchdowns) - (200 * interceptions) + (100 * completions) } / attempts ]. In 1979, when the NCAA developed the passing efficiency formula, they used average statistics from the previous 14 seasons of two-platoon football (which started in 1965).