Digital Signage Design Rules: Fonts, Contrast and the 3-Second Test

AI can make a sign look good in seconds, but it can't tell you whether that sign is readable on your screen, in your space. That part is still on you, and these are the rules I'd check before anything goes live.

They apply no matter how the sign got made: from scratch, from a template, or generated with AI. This is Part 5 of Design Beautiful Signs with AI.

Start with the 3-second test

Stand where your audience stands. Look at the screen for three seconds, then look away. Can you say what the sign was about?

If not, there's too much on it. This one test catches most signage problems.

How big should the text be?

A widely used rule of thumb is about one inch of letter height for every ten feet between the viewer and the screen. So a menu board read from 15 feet needs headlines around an inch and a half tall on the physical screen, and body text shouldn't get much smaller than that. When in doubt, go bigger. Nobody has ever complained that a sign was too easy to read.

Word counts to stay under

• Headline: about seven words or fewer.
• Supporting line: one short sentence, if you need it at all.
• Whole slide: if it's over roughly 20 words, split it into two slides.

Pick fonts made for screens

Clean sans-serif fonts are the safest choice. Use one or two per sign, not five. I'd avoid thin weights and all-caps paragraphs, since both get harder to read at a distance. Script and decorative fonts are fine for a single word of flavor, never for information someone needs.

There's more detail in our guide to choosing a digital display font.

Contrast matters more than color

Brand colors matter. Contrast matters more. Go dark on light or light on dark, with nothing busy behind the text. If you want text over a photo, ask for a solid or darkened panel behind it. Screens in bright rooms and windows lose contrast, so push it further than you think you need to.

Keep clear of the edges

Some TVs crop the edges of the picture, and people rarely look at the extreme edges anyway. Keep important text and logos out of the outer margins, roughly the outer five percent of the screen on each side.

Match orientation to the screen

Landscape content goes on landscape screens, portrait on portrait. A graphic built for the other orientation always looks off, stretched or letterboxed. When you generate with AI, say which one you need in the prompt.

How long should each slide stay up?

Long enough to be read twice. That's typically somewhere between 8 and 15 seconds, depending on how much text is on it. Keep playlists short enough that someone waiting in line sees the whole loop. A longer loop says more, but only if people stay to see it.

Build the rules into your prompt

The easiest way to apply all of this with AI is to ask for it directly. Add a line like this to any prompt in Display NOW's Create mode:

One short headline, very large and readable from across the room, high contrast, generous empty space, nothing important near the edges.

Readability questions, answered

What font size should I use on a digital sign?

About one inch of letter height for every ten feet of viewing distance, and bigger if you're unsure.

How many words is too many for one slide?

Roughly 20. Past that, split it into two slides.

How long should a slide stay on a digital sign?

Long enough to be read twice, typically 8 to 15 seconds depending on how much text is on it.

What is the best font for digital signage?

A clean sans-serif font in a regular or bold weight. Use one or two fonts per sign and avoid thin weights, all-caps paragraphs and script fonts for important information.

Related reading: spreadsheets on screen and menu boards. Then start a free trial and run these checks on your own screens.