“Now, I know you can’t read this”

Close-up of face of mature Caucasian businessman wearing shirt and tie and eyeglasses, looking at camera and squinting. Eyesight and optics conceptHow infuriating! You came for a presentation—but up on the screen are charts and words so small they cannot be read. You can’t find any meaning. And, just to rub it in, the speaker offhandedly tells you he knows you can’t read them.

What was he thinking? Obviously, nothing about the audience.

It’s an old complaint which, when you think about it, raises a reasonable question: how big should you make your font size? You don’t want to be “that guy,” the one who disrespects his audience with poorly designed slides. So suppose you’ve gotten religion and know better than to confront your audience with a wall of text or a long list of bullets. How do you display words correctly? You will probably emphasize images over words, of course. But when a slide does call for the written word (and sometimes it will) . . . how big should you make the letters?

For years, my rule of thumb was to use nothing below 22 points. I reasoned that if I needed to make the text any smaller than that, I was asking too much of the slide and should begin another one.

But Guy Kawasaki, the American marketing specialist, author, and Silicon Valley venture capitalist, recently suggested a more flexible rule you can make your own. It’s yours with three easy steps:

  1. Find or figure out in advance the age of the oldest person in your audience (after all, eyesight tends to deteriorate with the years)
  2. Divide that age by 2
  3. Use no font size below that number

Brilliant. This simple rule does several things. First, it makes you learn more about your audience. Second, it makes you mindful of their visual acuity. Third, it causes you to be thoughtful about the number of words you may place on a slide. And finally, it causes you to think anew about how words and images work together to engage your audience.