I've heard that you should wait 15 minutes for a professor who is late to a class, before leaving.

Some of my classmates have said that the 15 minute rule is only for professors without PhD's, and that you must wait at least 20 (and up to 30) minutes for professors that do have PhD's.

The PhD part seems silly, but after hearing some version of this "rule", or "myth", so many times, I wonder if it has some backing.

Is there any evidence that this was once an actual rule put in place by a university, or academic governing body? Was this ever anything more than a "rule" put it in place by impatient students?

Why wait?

Some classes will fail you after a certain number of absences and others will calculate 5% of your final grade from the percentage of lectures you attended. And it can be a good idea to attend as many classes as possible to show that you are putting forth effort. Professors are much more likely to bump a high D grade to a low C if they see that you have been to every lecture (at least in my experience).

So how long do you wait before the professor should no longer be able to show up and not give the daily "attendance credit" for absent students?

If a class was an hour long, and the professor didn't show up for 55 minutes, it would be common sense to leave by that point. But, at what point do you leave? An evil professor could always wait for 59 minutes before poking his head into the empty classroom and counting everyone as absent.

  • 4
    Why would there be any rules about this at all? Are these classes with mandatory participation? Is that actually something that exists at the graduate level? Commented Apr 30, 2016 at 4:52
  • Good question Tobias. I've added in the information to my question.
    – Matt C
    Commented Apr 30, 2016 at 5:01
  • 12
    "An evil professor could always wait for 59 minutes before poking his head into the empty classroom and counting everyone as absent." Please, be serious. A professor would get into huge amounts of trouble for skipping their own class and then trying to punish the students for not being there. Stop treating your education as a conspiracy against you. Commented Apr 30, 2016 at 7:55
  • 4
    Some universities have a written rule regarding how long you must wait for compulsory lectures or seminars. Commented Apr 30, 2016 at 8:17
  • depends on the country. In Italy it is expected that the professor will be 15 min late. In the Netherlands they will call the professor office if he/she is late by more than a couple of minutes.
    – Federico
    Commented Apr 30, 2016 at 9:15

3 Answers 3


The reason for the 15 minutes you have heard might be that in the past 15 minutes were allowed for both students and professors due to the imprecission of public time sources and the time to reach the lecture place. The term is still well known in some countries as an "academic quarter" ("Akademische Viertelstunde"). Sometimes it is still honored, but more in less official meetings. See https://en.wikipedia.org/wiki/Academic_quarter_(class_timing) The German version of the article says more about the history.

Todays there is no reason for this in regular classes and professors are expected to be on time. See other answers for recommendation what to do when they are late.

  • Where did you get that thing about "difference between the clock time and the solar time"?
    – Sverre
    Commented Apr 30, 2016 at 17:39
  • @Sverre I've heard it before, but only the Czech wikipedia mentions it so I have to confirm it somewhere else. Commented May 1, 2016 at 7:12

I'd suggest the following: wait 5 or 10 minutes, or whatever length of time seems to you to exceed an ordinary minor delay. Then call the department office and tell them that the professor has not arrived, and ask what they suggest you should do.

First of all, they may have some information about the professor's whereabouts or his/her likelihood of getting there, or they may be able to try to contact the professor. Otherwise, if they say you should leave, you have a pretty good defense if the professor should object. And if they say you should stay, you know that the department will not be on your side if you leave.


There is no such rule. The professor is paid, in part, based on a certain number of classroom hours. If they arrive late they are violating the terms of their employment, so it's hard to imagine them taking a punitive roll call after people had already given up. If this actually happened to you, ask the professor in question what they consider the right amount of time to wait.

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