<p>You can look up the class size distributions in each school’s Common Data Set, section I.
For example, at Yale, less than 3% of undergraduate classes have 100+ students. At Wisconsin, nearly 9% have 100+ students. At Harvard, it’s about 3%; at Michigan, about 8%. Cornell’s average class size averages are among the largest of any selective private school. Berkeley’s are among the lowest of any state university.</p>
<p>Do these overall averages reflect significant differences in the courses that most interest you? Or, are they inflated/deflated by concentrations of big/small classes in areas that don’t matter to you at all? Generally, required elementary-intermediate courses in the most popular majors or programs (such as pre-med) do tend to be relatively large at all research universities. Some universities (e.g. Berkeley, Wisconsin, Princeton, JHU) publish course enrollment numbers in their online course schedules for each term. You can use these schedules to compare enrollments for the classes that most interest you. </p>