Most PowerPoint designers love to have white space on their slides, but there will always be demands from clients to include more and more content. Now, this is not a great idea because slides need to be aesthetic and focused–and adding so much more textual or any other content negates the very idea of well-designed slides. Adding extra content is, therefore, a compromise that you should avoid.
In the real world, there will be many reasons to cram this content, and the immediate result is that designers have to use a font size that’s smaller than what they started with. But really speaking, what is the smallest font size that you can use?
There is no definite answer to this question, and as a rule of the thumb, you will want the minimum font size to be 24 points.
However, by declaring 24 points as the minimum font size, I may have opened a can of worms. There are so many other factors in play here that I cannot recommend any rules. You may, however, like to understand some guidelines:
1. Start With the Largest Font Size
Let’s start with the largest point size — this can be 44 points for slide titles. Most PowerPoint templates built within the program use the largest point size as anywhere between 36 and 54, but don’t believe that PowerPoint templates that Microsoft built inside the program are design landmarks set in stone: ) 44 points, though is a good rule of the thumb for slide titles.
2. Explore Largest Non-Title Text Size
I would then look at the largest text size for the rest of the slide, such as body text. Around 32 points (anything between 28 to 36 points) is a good size.
3. Now Decide the Smallest Font Size
For sub-bullets or text in the lower hierarchy, you can go down two levels and make them 28 and 24 point size respectively. This is exactly how I arrived at the minimum font size suggested at the beginning of this post.
4. Go With Smaller Font Sizes for Less Iimportant Stuff
But what about disclaimers, warnings, etc. that you must add to your slide just because your legal team asks you to do so? There is no reason to make them 24 points. Even something as low as 8 to 10 points will do for them. If your audience has to squint their eyes to read them, you might as well make sure they can’t read them at all! After all, no one needs to read that stuff. And if they need to, you can always email a PDF copy of the presentation to them.
5. Not All Fonts Are the Same
Do remember that these point size recommendations are faulted! Why? That’s because 24 point Arial is much larger than 24 point Times New Roman or even Calibri. You remember that I told you these were guidelines and not rules!
6. Make Exceptions
Yes, you can go down a wee bit lower than 24 points if needed. But limit these changes for a few slides, and only when absolutely essential. Remember that the slides were created for the audience. The audience was not created for the slides. You must, therefore, make sure that the last person in the room can read the slides.
7. Use Less Text
It is amazing how this guideline automatically lets you use larger-point sizes because you don’t have too much text to cram on a slide anymore!
8. Use More Pictures
That will again help you create slides with larger and lesser text.
9. Text Exists Beyond Text Boxes
Remember that text size is not limited to the text in boxes and placeholders. Text size is also important in charts, SmartArt, tables, etc. Most companies use slides with teeny-weeny text in these slide objects. At times, this will need a company-wide overhaul in design ethics. Maybe, it’s time you made a start in the right direction.
10. Learn to Break the Rules
So follow all guidelines, but there will still be times you will have to act against these guidelines. Maintain a philosophical attitude and try your best.
For many of you who have visited an ophthalmologist to check your vision, you must have seen a chart where the text diminishes in size in each subsequent line. In some ways, you have to treat your audience as someone who is visiting an ophthalmologist, but you cannot show them the smallest font size they cannot read! You have to make sure that every person in your audience can read all the text you want them to read. In other words, your alphabet chart should never contain font sizes that someone may fail to read. Of course, this alphabet chart is your slide!
This question about the smallest font size for PowerPoint slides or slides in any program was originally sent to me as an answer request on Quora. I expand my answer above.