(Note: This originally ran on CPATechViews.com)
How many presentations have you been to – or even produced yourself – in which the type was too small to read from across the room or there was too much on a slide to be able to read anything at all?
This is a rhetorical question, of course, because we all have seen terrible presentations from able, smart presenters who think they have to cram as much information on a slide as possible. A 10 column Excel file? Sure, no problem.
How large should the type be? My standard answer is no smaller than 24 points.
I didn’t just dream this up. There’s scientific evidence known as the “8H Rule.” Here’s part of the explanation from PPfaq.com:
The 8H rule says that the maximum viewing distance shouldn’t be more than 8 times the height (H) of the screen; if that condition is met then as long as your text is at least 1/50th the height of the screen, then it’ll be legible at the maximum viewing distance. That assumes that the person in the back row has good eyes, that the projected image is perfectly crisp, and that no other factors interfere. And it’s an absolute minimum, not a recommended size.
A normal screen show slide in PowerPoint is 7.5 inches or 540 points tall, so the absolute, don’t go below it minimum text size would be 540 / 50 or roughly 11 point text. For 35mm slides or good quality overheads, that’s not unreasonable. For screenshow projection, it’s wildly optimistic. You simply can’t form legible text at this height … roughly 12 pixels … in most fonts. For projected 800×600 screens, I’d at least double that, or use 1/25th the screen height to determine minimum text size. That translates to roughly 22 points. Use 24 points to give yourself some extra leeway in case projection conditions or your audience’s vision aren’t perfect (they won’t be).
Now to the question of how much to put on each slide and the font itself. Use something easy to read that is san-serif (block type without the ends of letters versus something more ornamental); I prefer Tahoma and Verdana.
Your PointPoint slides should be simple keyword concepts rather than complete sentences so you can avoid the trap most speakers fall into: reading their slides. However, if you must put bullets with sentences on the slides, use no more than four bullets per slide. The human mind can’t comprehend much more than that.
Now, I have no scientific evidence to support the 4-line rule – it’s the Cytron rule. Again – think of simple slides with images and keywords rather than too much type.
Here is one good and one bad example of what I’m talking about: