11 musts for highly legible slides

The proper typeface, styling and point size are essential to helping your audience see and read your text. There’s more, though: Pay attention to colors and contrast, too.

When your presentation ends, what would you like your audience to think?

  • “Those slide fonts were awesome! So innovative! So artistic! So shadowy and provocative!”
  • “I didn’t notice the slide fonts.”

It always surprises me when speakers want their slide fonts to stand out, as if it were reasonable compensation for a lack of compelling content.

Great slide fonts are easy to read and otherwise not noticeable. You want your message—not your slide fonts—to stand out and be memorable.

If you must have text on a slide, how can you best present it? The table below summarizes the guidelines. Read on for details and practical examples.

Make it legible—from the back of the room with tired eyes late in the day.

Where do you design your slides? On a desktop computer with a sharp 24-inch monitor? On a laptop, perhaps? Is your head within 18 inches of your screen? Is the room lighting good? We design slides in fairly optimal conditions with rich displays providing excellent contrast.

Your slides are rarely viewed in optimal conditions. The screens are small. The rooms are large. The projectors always seems to be dimmer and blurrier than you would like. And someone in your audience was up late last night. Or is suffering from allergies. Or is behind on their optical prescription.

When you add it up, the text on your slides is much harder to read than it seemed when you created them. Be smart. Design your slides with the largest and most legible fonts possible.

Be consistent.

Which sends a better message…

  • A slide deck that resembles a patchwork quilt, with typefaces, point sizes and styles randomized on every slide?
  • Or a slide deck that uses a consistent visual theme, including text that looks the same on the first slide, the 17th slide and the last slide?

Consistency matters. When your slide deck has a consistent design, your audience doesn’t have to work hard to understand the slide. They are free to focus on your message.

Download the free white paper, “Creating a Consistent Message,” to discover how to keep your organization’s message and voice on track across all your internal communications platforms.

Use large fonts.

Every time I teach my presentation design course, I conduct a test using the slide below. I ask everyone to stand, and then begin to call out line numbers from the top of the slide (1, 2, etc.), as I reveal one line at a time. I ask the students to sit down when they can no longer comfortably read the text on the slide. Can you guess what the results are?

Most people in the room remain standing until about line 8 or line 9 (18 point or 16 point). The interesting thing is that invariably at least one person sits down at line 5 (28 point).

What does this mean? For the conditions where I teach (room size, screen size, projector quality, etc.), I have to stay above 28 point text if I want everyone in my audience to be comfortable.

When I design my slides on my desktop computer, 30 point seems enormous. Yet that is the size that works for my whole audience.

Choose three sizes or fewer.

So, all your text is going to be large. Great. Does that mean it all should be the same size? Yes and no.

  • Body text should be the same size throughout the slide deck.
  • Slide titles should be a little larger than the body text, but the same size from slide to slide throughout the deck.
  • Text used in tables and figures can be a little smaller than body text.

This three-tiered system is familiar, because other writing follows a similar pattern. For example, in a typical book, headings tend to be larger than paragraph text, and paragraph text tends to be larger than the text used for annotations.

For a course I recently taught, I used 44 point for titles, 36 point for body text, and 30 point for annotations:

The room where I teach may not match the one where you speak, so you may have a different scale.

Use sans serif fonts.

Font faces are generally classified into two categories:

  • Serif faces are composed of line strokes that vary from thick to thin and have ends that terminate with decorative serifs.
  • Sans serif faces are composed of line strokes with an even width and have plain ends.

Serif fonts are generally acknowledged as superior when printed, so they are a great choice for your handouts. However, the serifs and thin strokes don’t always look crisp on digital displays. Although you can succeed with either serif or sans serif fonts, I recommend you adopt sans serif fonts for your slides. They have better legibility across a variety of display conditions.

Choose a font appropriate for your audience and message.

As a general guideline, choose a formal, professional font. Any of those shown above (Tahoma, etc.) are fine for this purpose. These fonts won’t undermine your credibility, and that’s the goal.

Font styles to avoid include artistic, playful, funky, script and many others—unless your audience or message makes this a match. If you break this guideline and use a specialty font (for branding reasons, or to tie into your overall theme), then understand the consequences. It won’t be as easy to read. It could be distracting. Only you can judge whether it is worth it.

Use one or two typefaces-at most.

Just like the guideline for using consistent font sizes, you should use consistent typefaces. Make this choice:

  • Choose a single face for all your text in a slide deck (as I do most often).
  • Choose one face for titles and another for all other text.

Using any more than two typefaces or using them inconsistently from slide to slide can make your slide deck look disjointed and awkward.

Never use word art, 3-D effects, shadows, warping, etc.

When I see slides with these types of effects, speakers usually say they are “trying to jazz up their slides” or “add some visual interest.” That’s misguided.

These font decorations reduce your text’s legibility considerably and accomplish nothing.

Use boldface, italics or underlines sparingly.

Boldface, italics and underlining are all used to emphasize text, but you shouldn’t use all three.

  • Underlining tends to reduce legibility because it cuts through descenders, like those in g, j, p, q and y.
  • Italics looks very sharp with some fonts (especially serif fonts), but it looks poor with others (especially sans serif fonts). So, if you are using sans serif fonts (as you should), italics may not be the best option.
  • Boldface tends to work the best of the three for emphasizing key words or phrases. This is what I use most often on my slides.

Whatever your preference, choose one for emphasis and use it sparingly. If you emphasize too many words, the net result is that nothing is emphasized.

Ensure high contrast between text and background.

Two universally successful strategies for high contrast are:

  • Black text on a solid white (or off-white) background
  • White text on a solid black or dark blue/green background

Sadly, many speakers use a variety of lower contrast combinations:

  • Grey text on either white or black background
  • Light blue/green/red/yellow/brown on a white background
  • Any text on a wildly textured background

Don’t make your audience strain to see the text.

Use additional colors for emphasis only.

Start by choosing a single text color, and use it consistently across all slides. Optionally, add a complementary color, either for emphasis or for titles, but use it consistently throughout your slide deck.

Never randomly change colors from slide to slide or within a slide with the misguided goal of “adding visual interest.” You will just confuse your audience.

I recommend simple color schemes that offer high legibility:

A version of this article first appeared on Six Minutes. Contact him on Twitter @6minutes.

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