The answer to your question will vary by school, year in school and individual study style. I can't even give you a personal estimate since I don't punch a clock. I try to get most of my studying done between 8-5 M-F. If I have an hour or two between classes (and I usually do), I'll find a place to get some studying done. If I'm done with class at 2:00 PM, I'll go to the library and study for a couple or three hours. Weekends are the time that I do all the "as needed" studying and assignment finishing.
So far, I've had a fairly normal life, but then again, I don't work (for now). My feelings might change when I start doing pharm intern work in addition to school.