When it comes to font, there are two important aspects: The font type and the font size. The first one is easy: Use Arial. It is simply the best font type for Powerpoint. Other sans-serif fonts like Calibri or Candara are also ok, but Arial still works best. Please do not use Times New Roman because you are used to it from MS Word – it just doesn’t look good in Powerpoint, neither do other font types with serifs. And don’t get me started on “fancy” font types like Comic Sans MS or Lucida Handwriting!
This brings us to the second topic, which is the font size. This is much more difficult to answer since there is no “right” size. In some Powerpoint tutorials, manuals or so-called “styleguides”, you will read some recommendations like “never use any font size smaller than 18 or no one will be able to read it” or something like that. That’s bullshit. The readability does not depend so much on the font size, but rather on the size of the screen the presentations is displayed on and on the distance between the screen and the audience. And, moreover, don’t forget that there are slides that are not presented to an audience, but are supposed to be read sitting in front of a PC monitor or in a printed version. So, believe me, there is no “no smaller than…” rule. In fact, it works the opposite way: There is a “no bigger than …” rule! No bigger than 24. That’s the biggest font size you should apply anywhere on your slide (apart from the title page, maybe, and even there you don’t need anything bigger than 40), and even this is only recommended for the slide title. Why shouldn’t you go bigger than that? Well, it just looks disproportional. A Powerpoint slide has certain size that is fix and can’t be changed. So it’s just natural that there is a maximum size for font to look good before it seems to be out of scale.
Here’s my general recommendation for font sizes:
a. Title/header of the slide: Between 16 and 24
b. Action title (What’s that?): Between 16 and 20
c. Header of a text box (What’s that?): Between 12 and 18
d. Text in a text box: Between 10 and 16
e. Foot notes: Between 6 and 10
Two final notes: First, once you’ve decided for a certain pattern of font sizes, stick to it. If you use size 14 for your text boxes, it’s always 14 and not 12 on the next slide and 16 on the following. Consistency is key. And second, the size of your fonts naturally should become smaller from the top to the bottom of the slide. This means that your slide title is the biggest font size, the action title is slightly smaller. Headers of text boxes are smaller than the action title and the text in the text boxes is, of course, smaller than the header. I know it sounds self-evident, but unfortunately, it’s not…
Check the following examples: