Class Size in Online Courses: What the Research Says

Barbra Burch, QM Manager of Research & Development

“While research has established that class size does make a difference, the question of optimal size still needs more exploration.”

Creating an optimal learning experience is ever-present in the mind of an educator. One aspect of that is class size. In other words, what is the ideal number of students in an online class to create purposeful instructor-student as well as student-content engagement (Moore, 2019)? The answer — it depends! 

When discussing optimal course enrollment size, several factors need to be considered, including course design. For example, courses designed from a constructivist perspective, with heavy discussion activities, will likely need to have lower enrollments in order to avoid too much cognitive load for learners (and the instructor!). That being said, some course designs and contructivist approaches might rely on automated feedback or breaking into learner-guided groups. In those cases, a higher enrollment could work. The guiding learning perspective for the course must also be considered. For instance, a course that aligns objectives, activities, and assessments with gaming technologies might be effective with a larger class size than one designed for scaffolding critical thinking as guided by the instructor. 

While there is no easy, cookie-cutter answer to the online class size question, research supports the fact that it is an important consideration. Class size can be a factor in a student’s course experience and outcomes, as well as in an instructor’s experience teaching a course (Lowenthal, Nyland, Jung, Dunlap, & Kepka, 2019). The reason for this is that class size is positively correlated with the amount and quality of interaction between instructors and students in the course (Parks-Stamm et al., 2017). Although class size can make a difference to students and instructors, it’s important to remember it is only one of many variables related to the course that has an effect. While research findings on optimal class size vary (Sorenson, 2015) (Taft, Perkowski, & Martin, 2011), some recommended size ranges appear again and again, depending on the type of course (e.g., lower-level vs. advanced), the goals of the course (e.g., survey vs. writing-intensive), and the amount of prior experience the instructor has with online education. 

So what does the research indicate about optimal class size? Sieber (2005) recommended a class size of 12 for instructors new to teaching online; Tomei (2006) also recommended a class size of 12 in relation to the course level (for a graduate-level course) rather than the amount of experience the instructor had teaching online. Colwell and Jenks (as cited in Burruss, Billing, Brownrigg, Skiba, & Connors, 2009) set the upper limit for a desirable class size as 20 for an undergraduate course and between 8 and 15 for graduate courses (p. 34). Burruss et al. concentrated on finding the class size that fostered the correct balance of interaction in the course — not so large that students feel lost and disconnected and not so small that there are too few opportunities for interaction (p. 39).  Yet, Lowenthal, Nyland, Jung, Dunlap, and Kepka (2019) pointed out the likely push from administrations to teach high-enrollment online courses.   

Parks-Stamm et al. (2017) looked at student and instructor posts and interactions in 500 online courses to find factors contributing to those interactions. They found that both class size and the amount of instructor participation had a significant effect on interactions and that these factors were related to each other. While the amount of instructor participation did not predict the number of posts per student in courses with 15-30 students, courses with fewer students showed significant differences in student participation depending on the amount of instructor participation. In other words, in the courses in this particular study, student interaction in classes of 14 or fewer students increased when there was more instructor participation.

While research has established that class size does make a difference, the question of optimal size still needs more exploration. In the meantime, how can you know if your class size is working? One of the best ways is to look at student performance. Many factors can impact student performance in a course, but low grades and high withdrawals can be a sign that the class ratio isn’t working, especially as the course is currently designed. 


Arzt, J. (2011, October 21).  Online courses and optimal class size:  A complex formula. Retrieved from

Burruss, N. M., Billings, D. M. Brownrigg, V., Skiba, D. J., & Connors, H. R. (2009). Class size as related to use of technology, educational practices, and outcomes in web-based nursing courses. Journal of Professional Nursing, 25, 33-41. DOI: 10.10.16/j.profnurs.2008.06.002.

Haynie, D. (2014, September 26). Experts Say Class Size Can Matter for Online Students.  Retrieved from…;

Lowenthal, P. R., Nyland, R., Jung. E., Dunlap, J. C., & Kepka, J.  (2019). Does class size matter? An exploration into faculty perceptions of teaching high-enrollment online courses.  The American Journal of Distance Education, 33(3).  152-168.  Retrieved from 

Moore, M. G. (2019). The theory of transactional distance. In M. G. Moore & W. C. Diehl (Eds.),  The Handbook of Distance Education, (4th ed.) (pp. 32-26). NY:  Routledge

Parks‐Stamm, E. J., Zafonte, M. and Palenque, S. M. (2017), The effects of instructor participation and class size on student participation in an online class discussion forum. British Journal of  Educational Technology, 48: 1250-1259. doi:10.1111/bjet.12512

Sieber, J. (2005). Misconceptions and realities about teaching online. Science and Ethics, 11, 329-340. Retrieved from

Sorenson, C. (2015). An examination of the relationship between online class size and instructor performance. Journal of Educators Online, 12(1), 140-159. Retrieved from

Taft, S. H., Perkowski, T., & Martin, L. S. (2011). A Framework for Evaluating Class Size in Online Education. The Quarterly Review of Distance Education, 12(3), 181-197. Retrieved from…;
Tomei, J. (2006). The impact of online learning on faculty load: Computing the ideal class size for online learning. Journal of Technology and Teacher Education, 14, 531-541. Retrieved from