I spent a summer at Stanford Med as part of a program, and the Dean of Admissions told me that Stanford (along with a "group of elite" medical schools, including Ivies) has a minimum cutoff of 27 MCAT and 3.3 GPA (didn't say if it was science or cumulative). In terms of other "formulas", combinations or algorithms used... I have no idea.
Below those numbers... you'll be giving free money to the schools for secondaries while your application is tossed to the side. In terms of the UC's, USC and Loma... no clue.
Best of luck!