I’m pretty old-school when it comes to this question having worked at colleges for the past 17 years. Personally, I recommend 7. Two “reach” schools, three mid-range schools, and two “safety” schools.
A “reach” school is a school that you would love to attend, but you’re not quite sure you have the chops to get in. Maybe, your SAT is a bit lower than their average SAT. Or, maybe your high school GPA is a bit lower than the average applicant. Whatever the reason, I still encourage students to shoot for the stars (within reason) and not discard two top choice schools because of one thing missing from their background/application.
Mid-range schools are schools that fall within your academic background, offer the major you want to study and all around provide an environment/campus that you’d be happy attending. A mid-range school is not a slam-dunk, but there is a very strong chance that you will get in based on your background, fit and academics.
A “safety” school is pretty much self-explanatory based on the name. It’s a school that you are confident that you will get into based on your academic profile and background. Make sure that the safety schools you pick are still schools you’d be happy to attend. Don’t think of them as some sort of last resort, because they aren’t. Many students attend their safety school because of location, convenience and/or cost.
Before applying, be sure that you would be comfortable attending any/all of the universities that you have selected and do not put all your hopes into one school. That can sometimes,be a recipe for disaster and why put yourself in that position.