Does Williams College or UC Santa Barbara have smaller class sizes overall?

Williams College has smaller class sizes overall. It is a small liberal arts college built around close faculty interaction, and its signature tutorial system often puts students in classes of just two people at a time. UCSB, by contrast, is a large public research university, so undergraduates are much more likely to encounter bigger lecture courses, especially in introductory subjects.

In practice, Williams is designed for discussion-based teaching across the curriculum. A large share of classes are small seminars, and even outside tutorials, the classroom experience tends to be centered on direct participation rather than large lectures.

At UCSB, class size varies much more by department and course level. Upper-division classes can become fairly manageable, but many first-year and lower-division courses enroll far more students than you would typically see at Williams, and discussion sections are often led by TAs alongside the main lecture.

For an undergraduate who prioritizes consistently small classes across most of college, Williams is the clearer answer. UCSB can still offer smaller settings later on or within certain majors, but overall it does not match Williams for a small-classroom experience.