As a faculty member at the University of Oregon I taught a wide variety of undergraduate and graduate students. There was a “rule of thumb” that undergraduates were expected to spend two hours of time studying outside of class for each hour in class, and that graduate students were expected to spend three hours outside of class for each hour in class. The rules of thumb were in reference to courses that had one hour of class meeting per week for each hour of credit in the course.
Over my years of teaching, I gradually became suspicious that many students were not paying much attention to such guidelines. When my wife’s daughter began attending the University of Oregon a little over 15 years ago, she reported that her undergraduate peers seemed to be doing about one hour of work outside of class for each hour in class.