Recently I have come across an infographic on public speaking that mentioned font size. The statement is clear: The 30pt rule. Don’t use text smaller than that or the audience will not be able to read it.
What is the right font size for your slides? Is the 30pt rule correct?
First of all here we are talking about slides you are going to show the audience during a presentation, handout documents in a slide format (slideuments) are a different thing.
I don’t believe strictly at the 30 points rule, already seen sometime ago as 32pt rule also as 32 for title and 24 for body. I don’t think there is a fixed number that works always, readability is the key issue. It depends on font type, contrast with the background, how close is the public and several other factors. Surely a font in 64 points is more readable than one in 12 points. A funny rule, albeit not orthodox, goes like this: “check the age of the oldest in the room, halve it and that’s your minimum font size”.
In my public speaking courses I often run an experiment; I show participants a slide with text in different sizes, like the eye chart you may find in an optician, then I ask them what they think is the most appropriate text size. After that I ask what font size they use for their presentation. In the vast majority of the cases, the one they voted on screen is twice the one they normally use. I am thus inclined to say that it’s a good practice to enlarge text.
A larger font size offers a valuable benefit, you are left with less space to write, and less text on slides is a good thing. Try using a 120pt font and surely you’ll have little text in your visual aids. You can find inspiration in the Takahashi method or Lessig method.
To sum it up, I do not adhere to the 30pt rule as an absolute value, keep in mind some useful suggestions:
- Text should be easily and immediately readable by everyone in the audience
- Too much text on slides is not appreciated
- Bigger text has greater visual impact
With these consideration it’s difficult to understand why using a small font. It decreases readability, it’s an incentive to write more and has a lower visual impact.