What limits the number of PhD students in universities with and without PhD tution fee? Universities normally (as far as I know) do not limit the number of PhD students a research-active professor can have as long as he secure the funding for his PhD students. For example, if a professor have enough research fund can get 10 PhD students (instead of research associates) and pay them directly. Then, they pay their tution fees, and university/department can increase its capacty for PhD enrolment.

In fact, the university/department can increase its capacity as long as they are paying students, but I don't understand how this scheme works when PhD study is free (in some European countries).

In the latter case, the professor provide research funding for the PhD projects and their wages, but the university should invest for courseworks (pay more teachers for these unexpected students).

What limits the number of PhD students in universities without PhD tution fee?

And when there is normal tution fee, isn't there any limitation for the number of PhD students as long as there are good candidates?

EXAMPLE: A department arranges the admission of 10 PhD students (assigned appropriate professor for the courses). Now, a professor fund 10 more PhD students for himself. Now, the department head should plan new classes/courses (this needs budget). He may need more resources, which is normally approved by the Dean.

I understand that more PhD students fuels the engines of an academic unit, but the department head is not bothered with overload of PhD coursework. In other words, does the department head encourage professor to get more funded PhD students, and saying "don't worry, I will take care of coursework"?
What limits the number of PhD students in universities without PhD tution fee?


I'm not sure countries exist without a PhD tuition fee. Rather there is a scholarship system in place to cover the cost of tuition. The limiting factor here is the number of scholarships allocated by the government. So the answer is the government.


  And when there is normal tution fee, isn't there any limitation for the number of PhD students as long as there are good candidates?


This would be dependant upon the institution. There may be a hard limit imposed by the faculty. Otherwise there is a soft limit in the number of students one professor can reasonably manage.