<p>UIUC uses class rank as a key factor for admission. How it translates into a GPA simply depends on high school. 84% to 96% translated the other way simply means you are in the top 16% to top 4% of your high school class. If your high school does not rank, UIUC estimates it based on your GPA and its historical knowledge of your high school and applicants therefrom. Note that many high schools that do not rank actually do send colleges a psuedo ranking in the school’s profile sent to colleges. For example, they may tell the college that top 10% of class has a 3.8 GPA or better, top 25% has a 3.3 or better, etc. (those numbers are just examples).</p>