In a math talk (at a seminar or a conference, not teaching) that uses projected slides, is it better to display the number of slides left or not? What are the pros and cons? Some people tell me they like it, others prefer when it doesn't appear. I'd like to have some objective comments about this.

For some context, talks in math are typically one hour long, so the number of slides can be large. I like to cut talks into a few short sections. Right now I'm using the following layout, displayed at the top of every slide (from the "Frankfurt" beamer theme):


The current slide in the current section is highlighted, as well as the title of the current section.

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    @AustinHenley: Well then, do not count those animation-slides as individual slides. LaTeX Beamer, for instance, takes care of that automatically when creating slides with multiple steps. Sep 14, 2016 at 16:59
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    @O.R.Mapper In that case, my last talk would only consist of 3 slides. I don't think that is very useful information. My point is that we are beyond the era of physical slides. Sep 14, 2016 at 17:04
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    @AustinHenley: But we are not beyond the era of asking questions that refer to specific things that were shown in the presentation. Hence, reasonably fine-grained reference points distributed across the presentation are indispensable. A convenient manner of providing such reference points is by consecutively numbering discrete units in the presentation (the total number of which is then trivial to determine and display). If you can find only three of these, your presentation is probably not yet sufficiently structured. Sep 14, 2016 at 17:33
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    @AustinHenley And as you can see, mine has 21 standalone slides (not counting the title etc), not three; and almost all of them are broken up into several actual slides and I obviously don't count them as independent. I don't think I've ever seen an hour-long math presentation with only three slides... Are you in math and are your talks one-hour long?
    – user9646
    Sep 14, 2016 at 18:14
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    @AegisCruiser: If you have read the above comments, you have learned that there are ways to ensure exactly this is not the case despite using animations. Sep 14, 2016 at 19:23

9 Answers 9


Halmos advises that in preparing a talk you should have a block of material that you can omit if you are running short of time. But if the slides show number of pages left, you cannot do that invisibly. For example: in an hour lecture, if you are 5 minutes from the end of the hour, but your numbering shows you are only halfway through your slides, the audience will be getting restless.

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    Interestingly, I have been taught that bringing slides that you end up not showing is a sign of a bad preparation and should be avoided at all cost. The fact that you have to drop an otherwise possibly helpful piece of information for exactly this reason seems to confirm this stance. In any case, when we're talking about a lecture (about the only kind of talk where I really see why exact planning of the duration might not be desirable), the slide number refers to the chapter, without any guarantee that the chapter will be finished within the current lesson rather than continued next time. Sep 14, 2016 at 13:39
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    A mathematics talk may allow questions and discussion to occur during the lecture. But Halmos' ideal lecturer would finish on time anyway, and the audience would not know something had been omitted.
    – GEdgar
    Sep 14, 2016 at 13:47
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    Sorry, but I don't get this. If you think that you want to jump over something in your talk, just say what part you skip and then jump over it. People will notice that you jump over some slides anyway, and the fact that the page number jumps will not distract anymore than the fact that some slides are skipped. (As a side note, the advice of Halmos is some decades old. I find most of it still very helpful, but since technology has advances and presentation style has changed, it should be perceived as anywhere near authoritative…)
    – Dirk
    Sep 14, 2016 at 18:30
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    Also, the fact that the people in the audience get restless if you have too many slides on the clock is a feature not a bug…
    – Dirk
    Sep 14, 2016 at 18:31
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    This is not a good enough reason to base this decision on. It's perfectly fine if you tell your audience that you're skipping some slides for time. Nobody will hate you for it.
    – Peter
    Sep 15, 2016 at 11:00

A method to please both probably exists. Just tug a #/## at the lower corner, with the first number being the current slide number and the second one being the total slide number. People who have question on a certain slide can jot down the number quickly and come back (rather than "Can you go back to the third dot under 'The Model?'"); people who find a large bar intrusive will be less likely bothered by some small numbers at the corner.

I personally don't have problem with how beamer displays the time-line; it looks elegant. (I sometimes use it just to be that "lone kid in the department who uses LaTeX.") However, it requires some skills to be truly effective. Too many times I have seen very long section names used in this device, which clutter up the time-line badly.

And to be honest, I'd rather save the area on the slide to arrange information beautifully for those who pay attention then to give up 10-20% to set up a device for those who doze off and want to hop back in. Even I do care about them, major section signposts do not need to be on the screen all the time, the speaker (or a transition slide, or a small phrase next to the #/## index) can also deliver the transition.

Disclaimer: I don't give math talks, I work in biomedical field.

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    The navigation thing takes up less than 5% of the slide, I don't cram them with so much information that I need that space to arrange it better, I think... Besides, I actually wasn't really thinking about people who dozed off but rather so that people know approximately where I am in my talk. Would you say that this kind of aid doesn't actually help? I've added a link in my question if you want to see how a full slide looks.
    – user9646
    Sep 14, 2016 at 12:51
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    The need to arrange information does not necessarily mean it's crammed; white space is a powerful design factor as well. Everything on the screen is signal or noise. If that timeline bar may sometimes become noise, I'd rather not use it. I'd strive (totally not there yet) to work on a talk that people wouldn't want to wonder how long it'd last or which section I am at, but rather being engaged with my contents. That bar acts like a reminder (to me) that this talk is just another process to go through. Anyhow, it's a matter of style and I'd say do what you feel right. We can't please all. :) Sep 14, 2016 at 13:06
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    @Penguin_Knight: It's a common misconception that the only purpose of a timeline bar (or any indicator that shows "how many slides there are to yet to come") is to know how much more time the talk will go on for. I always find the information about the total slide number/progress within the talk to be crucial because it helps me have some orientation within the topic. Based upon the relative position, it is much easier for me to sort the currently presented information (that I may be very engaged in) into my mental model of the subject. I consider a desire to do so a positive sign for a talk. Sep 14, 2016 at 13:16

I would always use a

current page/last page

setting. Additionally, you should have an outline of the talk the help the audience to navigate through your talk (but not to spend five minutes of the talk to read out your outline).

This helps the audience to keep track of where they are, and also help the chairperson of the session to see where you are going with your talk. When I am a chairman, I usually get nervous when a speaker has no outline and no page numbers and his time is running short. I then keep asking myself, when I should interrupt the speaker and it usually turns out for the worse of the speaker…

But you need to keep a few things in mind:

  • The number last page should really be the number of the page that you want to display last. If you have any back-up slides after that, insert the correct number manually, e.g. by \renewcommand{\inserttotalframenumber}{22}. You may or may not restart the frame counter after that last official slide.

  • Make sure that each counted frame/page is really one page. I've seen a talk that had ~100 "official frames" but more than 80 of them showed a single image that was part of a movie.

  • Train you talk such that you don't have to omit something. It's a matter of preparation and can be done. Put in time, effort and also practice your talk to get the right timing. While you plan, keep in mind that you may have questions during the talk.

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    + if someone has a question, (s)he can start it with "On slide 18, you said that…", which is really handy (as opposed to both nothing, and to "on Section 3.4").
    – Clément
    Sep 14, 2016 at 17:34
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    @NajibIdrissi Well, 18 refers to slide 18 - pretty easy to jump there. 3.4 refers to some slide - could be anywhere between the first and the last…
    – Dirk
    Sep 14, 2016 at 18:24
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    Oh, you understood that Section 3.4 equals to the forth slide of section three. Agreed, then this is pretty easy. But as a matter of fact, most people in the audience do not memorize which dot is which slide but do memorize page number easily (On a different note, most presenters are not aware that the dots are actually links (as many other things in beamer are actually links but no one seem to use these).)
    – Dirk
    Sep 14, 2016 at 19:27
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    @NajibIdrissi People wanting to point to a specific part of your talk want to be accurate, and don't necessarily remember the structure of your talk. General questions don't need to point to a specific part of your talk ("Why is this approach sensible?"), detail-oriented questions ("why is this equation valid?") are more likely to be understood if there is a specific slide to support them ("On slide 18, why is the equation in the middle of the slide valid?" seems preferable to "Somewhere in Section 3.4, you had an equation, could you justify it?").
    – Clément
    Sep 15, 2016 at 2:40
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    I think we are getting toward extended discussion here… One last thing: When I see a slide I notice the page number instantaneously without thinking. When I get the impulse to note down that slide I can just write down its number without any thinking. If there are only dots and section titles, my brain has to do some additional work to get the number. Anyway, since you design your slides to make them as accessible to the audience as possible (do you?), then you should take the habits of your audience into account and most people are familiar with page numbers.
    – Dirk
    Sep 16, 2016 at 13:30

I would omit the slide count altogether; what is important is which topics you have covered and have yet to cover. For example, you might periodically show a slide that looks something like

x Topic 1
x Topic 2
  x Topic 2a
  * Topic 2b
* Topic 3

at which point you would indicate that you have completed talking about Topic 2a and will proceed to discuss Topic 2b. The fact that Topic 1 was already covered, and that Topic 3 is still to come, is implied.

Your audience already knows how much time you have been allotted for the entire talk; they don't need constant reminders about how much longer you will be talking. The purpose of the topic lists is not to let them know how much longer you will be talking, but to remind them how each section of your talk fits into the whole.

The point @Penguin_Knight raises about the slide numbers providing a point of reference for a question is valid. You can provide a slide number, though, without providing a slide count.

  • "You can provide a slide number, though, without providing a slide count." - but then, the slide number is only a point of reference for a question, not a point of reference for how "deeply" we are inside the core subject of the talk; so-to-speak, where we are with respect to the whole talk. Apparently, you do consider this information somewhat interesting for the audience, which is why you suggest to show the complete outline. I would argue that the slide count is a more convenient (due to permanent availability) way of knowing "how each section of your talk fits into the whole". Sep 14, 2016 at 17:45
  • There isn't necessarily any correlation between how long it takes to discuss a topic and how many slides are used for that topic. Topic 1 might be 3 slides that take 20 minutes; Topic 2 might be 30 slides that take 5 minutes. I considered the idea that slide titles might be a sufficient point of reference for an audience member, but acknowledge that a slide number is probably easier to note for later reference.
    – chepner
    Sep 14, 2016 at 17:52
  • I also concede that my idea of "30 slides that take 5 minutes" consists of a series of overlays such that you might only "number" a few of them.
    – chepner
    Sep 14, 2016 at 17:54
  • Well, I do not claim that knowing about the slide count is useful for knowing about how many minutes the talk is still going to last. I do not expect slides to take equally long to explain. What I have found to be somewhat reliable, though, is that - based upon the space available on each slide - presenters generally try to give each slide a certain focus and accommodate a certain number of key takeaways on each slide. The density/frequency of these varies, but is usually somewhat balanced within one presentation. With this in mind, the slide count helps determine the approximate ... Sep 14, 2016 at 18:06
  • ... overall information gain about the subject of the talk already covered. Sep 14, 2016 at 18:06

tl;dr: Show it. In the beginning, the audience will be "warned" if your slide cadence will be fast or relaxed. And both you and audience will know how fast your progress is. If you have two slides pending chairmen are usually well-disposed when you are running short on time. If they don't know they will more likely interrupt you and ask you for speeding up. If you add extra slides for discussion - tables, reference citations, more details, etc. do not count them to the pages counter. It is awkward to have "Thank you" slide with number 10/15.

For short talks (10-20 min) I ommit the outline part, because it is always Introduction - Experimental - Results - Conclusion setup. I believe that every field has its "typical pattern". And it also cost time I would like to spend elsewhere (Results).

I have modified the crane layout. Above the header there is the title of the speech and in the footer there is my affiliation, conference name and date and the page numbering.

For longer talks (>30 min) like plenary lectures, I would divide the talk into parts and adress them in outline. In that case I would also show th page numbering (page/pages) and small "progress bar".

Regarding GEdgar's point, having half of the slides pending when having 5 minutes left during 1 hour lecture is utterly poor timing and displaying page numbering is of lesser issue.

  • 2
    "because it is always Introduction - Experimental - Results - Conclusion setup" - indeed, and it is one of my pet peeves to try and make students recognize the sheer pointlessness of saying things like "I will start with an introduction." or "My talk will close with a conclusion." Sep 15, 2016 at 17:05
  • My answer takes the queston in general; my field is material science, therefore the experimental part. You, as a mathematician, face slightly different "typical pattern".
    – Crowley
    Sep 16, 2016 at 9:59
  • @NajibIdrissi Whether the subject is or is not math is irrelevant, I think. You also stated that the talk might be moderated and the moderator, aka chairman, can decide whether to speed you up or not.
    – Crowley
    Sep 19, 2016 at 9:01
  • @NajibIdrissi I have read the braced text "seminar or conference, not teaching" as indicator of (probably) moderated talk. According to these commens I think your question was inteded to adress preferrably the length of the speech than the field. I got it wrong, sorry.
    – Crowley
    Sep 19, 2016 at 13:28

In general user experience (human computer interaction, human factors, psychology) research, progress indicators are to let people know how long they need to wait or work to get a job done, and to allow them to determine if something has gone wrong, or if they thus need to conduct themselves differently (speed up, slow down). You already have a natural progress indicator built into your talk: the time. If your talk is one hour and there is 30 minutes left, the audience need only check the clock to see just how close you are to being done. The concern would be if you are suddenly going to be done early (and I don't recall ever being worried that any speaker was going to finish talking too soon), or too late (a very real concern), so a progress indicator would really only be useful to determine "on time, going over time, will finish early".

There is a second type of progress indicator available to you during a talk, which is...well, you. You can simply say things like "let me check the time...ah yes, we are right on schedule!", or "in the interests of time I'll omit some less interesting details here...", etc. You are providing the audience useful information they want to know, namely "will I need to prepare to walk out on this joker while he is still talking to get to the next talk on time", or at worst "can I possibly survive until the end of this talk...". Again, the time is the natural progress indicator here, so everything is likely to be judged relative to that.

In your proposed method of slide progress indicator, my question would be "what does this progress indicator add that the time and you as the speaker are not already providing?" What does your system provide to the audience, which they can not already determine trivially by context?

Other things your system could do is serve as a kind of mental map, allowing the audience to see how what you are saying fits into the talk as a whole. In most academic talks I'm use to, this is already provided both by the introduction/overview and the natural structure of talks. Unlike in website navigation, it is not assumed that your audience will get mentally lost, such as by getting up and walking off to get lunch and then expecting to pick up from where they left off (a big reason for such a progress indicator on a web presentation/form).

The biggest use I can imagine in this is actually not for the audience, but for you the presenter. At a glance you can see how you are pacing each section, and with some previously calculated mental math you can see if you need to speed up or slow down. The status indicator can also serve as a reminder to you of what is next, which can help you talk about the right thing at the right time and segway smoothly into the next slide and section. I know I personally regularly rearrange my talks as I revise them, and its easy to remember the order of the slides as it originally was and forget your last revision.

So in the end, based on my understanding of related research domains and personal experience giving talks and listening to them, I don't think the progress indicator of slides left/slide numbers is going to be a significant benefit to your audience. However, I do see how the system might be useful to you, and if it helps you give a better, more organized, more confident, smooth, useful talk, then that is of tremendous benefit to your audience indirectly and you should go for it! So long as you don't provide false indication, such as making it seem like you are going way too fast or too slow to make appropriate use of your time slot, then I don't think there is any real concern in choosing the system if you feel it helps you.

  • "In general user experience (...) research, progress indicators are to let people know how long they need to wait or work to get a job done" - yes, but those are progress indicators that are displayed while the progress indicator observer has to wait. The only goal of the observer is for the progress indicator to reach the end of the busy phase, and the only (non-interrupting) decision for the observer is between remaining completely inactive or remaining inactive just for the task at hand and doing something else meanwhile. Isn't a progress indicator in a presentation a completely ... Sep 14, 2016 at 23:17
  • ... different situation? After all, it is not telling the observer to remain inactive, and the goal is not reaching the end of the progress; it is providing an additional hint about the current state of the task (that the observer is very actively performing, by attentively listening to the presenter), and the goal is successfully concluding this activity - listening and finally having a complete overview of the subject and knowing whether or not something is missing - before the progress bar reaches 100%. Sep 14, 2016 at 23:17
  • "What does your system provide to the audience, which they can not already determine trivially by context?" - quite obviously, an explicit indication of the current semantic progress in the presentation topic, rather than having the audience resort to guesswork or even distracting calculations based upon the current time, the unannounced and somewhat irregular time the current talk started, both with respect to the total actual (delayed?) start of the current session comprising n individual presentations, mapped back to the expected contents distribution of the talk? Sep 14, 2016 at 23:19
  • @O.R.Mapper Progress indicators are actually a bit more general, and include things like on the top of forms when it says "step 2 of 4", timelines on the bottom of videos (which don't always support other uses, like scrubbing), etc, and are not always in strictly blocking situations. But the general rule is they provide useful feedback to guide a user's action - whereas an audience has a far more limited range of interaction options that are based on where a person is in their talk generally. It could be that the indicator...
    – BrianH
    Sep 15, 2016 at 2:13
  • ...gives the audience morale support for continuing to be engaged with the material, by showing progress and context of the talk. On the other hand, it violates the general guidelines of minimizing what is on a slide, and could increase cognitive load and distraction from the main content. Some situations could of course make the indicator more useful in a presentation, especially in a situation where people can't easily keep track of time - though I'm not great with time and still haven't really ever had a problem in a 1 hour talk, and imagine this could be a bigger help on longer sessions.
    – BrianH
    Sep 15, 2016 at 2:22

Would you like, in an exciting movie, to have a counter at the bottom of the screen, saying: "50 out of 90 minutes"? There may be movies that profit from this as a suspense build-up, but most of the time, this would be quite a distractor and very counterproductive.

No, tell a good story, build suspense, and develop your argument stringently, don't bore your audience with structure which may make sense post-hoc, but not pre-hoc. Ideally, make them ache for the next slide.

Of course, you yourself should ensure to be well on time, though, but take care of not turning this into the worry of your audience.

And, if you conclude a few minutes before the expected time, when expectation is still high, and people have not yet remembered to look at their watches, you've done it the right way (TM).

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    "Build suspense"? I've always been given the advice that people don't want suspense in scientific presentations. "Tell them what you're going to tell them, then tell them, then tell them what you've told them." I'm curious to hear a different perspective. Sep 15, 2016 at 7:32
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    'Would you like, in an exciting movie, to have a counter at the bottom of the screen, saying: "50 out of 90 minutes"?' - no, because in a movie, a surprising twist that shifts the focus, turns things into a new direction, or unexpectedly opens up a new adventure is a positive thing. In a presentation that is meant to convey information, I would consider this to be very negative. Sep 15, 2016 at 7:37
  • Of course, talks are about conveying information. But the very best talks I have ever attended, the one that I never forgot, were of this make; they reached from mathematics to biology or philosophy (so, the field doesn't really matter), and given by top representatives of the field. I should think that this is an ideal to aspire to. Of course, a "bookkeeping" talk is also doable, but in my opinion, unless it is about specific new methods, in which technical details matter (I discuss elsewhere), a talk should just be a enticing showcase of your work, inviting them to read your work in detail. Sep 15, 2016 at 9:36
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    @CaptainEmacs: I find presentations following that style quite unbearable. They usually make me wonder why the presenter does not simply tell the audience what they have found, and instead acts as if there were big secrets that are then suddenly revealed. I feel that each of these "surprising twists" kicks me out of my current thought flow and makes the mental model I had built until then crumble. On various occasions, such talks were a great encouragement to start the coffee break early. It is interesting to know some people actually seem to enjoy that presentation style, though. Sep 15, 2016 at 10:14
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    The response gets a lot of downvotes. I suggested the response because it tallies with my own experience, taste & style and I regularly get very positive feedback on my talks in person - however, since the downvotes are quite massive, and clearly many people here on SE strongly disagree with my response, I am tempted to delete it. I do not want to let advice stand that people clearly believe to be destructive, as good experience I've had myself with it and as little as I like numbered slides myself. I'd like to know what's the general practice on SE in such situations? Sep 15, 2016 at 23:51

Part of a good talk is good time management. If you have prepared well, including trying out your talk before it gets serious, you should have a good idea of how much time you will need and can adjust accordingly. You will even be able to get an idea how long you can engage with audience comments and questions. For the purpose of this answer, I will assume that your time management is good. If itisn't, you might as well just inslt your audience by swearing at them.

If your time management is spot on, you have two reasons for why you might want to display the number of slides left.

  1. You may want to make it easier for the audience to refer to some slide of yours. In that case, precise slide titles will serve this function better. I think it is easier to ask for the slide that gives the equivalents of the definition of a woolladuh than asking for slide 7.

  2. You may want to signal that our talk is on time. I think this is indeed legitimate in many contexts. In a conference where only short presentations are allowed, worrying that the speaker before you steals all your time might prevent you from paying attention. In a setting where people running out of time is a real possibility, I think the (number of current slide)/(number of total slides) works well, it gives the relevant information while minimizing the increase in noise. For a long seminar presentation, providing a roadmap of your talk will do more to ease your audience.

  • "I think it is easier to ask for the slide that gives the equivalents of the definition of a woolladuh than asking for slide 7." - it is definitely easier to jot down 7 than Definition of a woolladuh, for later reference during the Q&A part. And once written down, asking for slide 7 is trivial. Directly jumping to slide 7 again is, of course, trivial for the presenter, as well, while they might not immediately remember the exact position of the slide whose title is Definition of a woolladuh. Sep 14, 2016 at 21:42
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    To address your first point, it is enough to display "slide 7" rather than "slide 7/42", so I think it answers a different question. Sep 15, 2016 at 6:17

I would not display number of slides left when a) you have good reputation or goodwill with an audience (very interesting topic, you have been invited, people already heard your other talks) or b) your presentation will be approximately at a constant pace.

However, I would display number of slides left, if you are c) in the environment where many people (try to) go over their allocated time (e.g. conference) or if d) you have a slide for which you know will spend disproportionate amount of time on. But d) is best handled otherwise (e.g. split it into multiple slides), as you may get the opposite effect, depending where in the presentation such slide stands.

Number of slides left is to assure the auditorium "I know what I am doing, bear with me, I am aware of the time constraints", and if you then go over your allotted time it will look a bit silly.

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