Letter Visibility Chart: How Big Should Letters Be on a Sign?

When it comes to sign letters, bigger is usually easier to see. Pretty simple, right?

Well… almost.

A letter visibility chart gives us a good idea of how large letters should be based on how far away someone needs to read them. As a general rule, the farther your customer is from the building, and the faster they’re traveling, the larger and simpler your sign needs to be. There are several other things we have to think about before deciding how large those letters should be.

A letter visibility chart helps connect letter height with viewing distance. Large letters can be read from farther away, while smaller letters usually work better for signs viewed up close. That’s useful information, but every property is different.

A sign facing a slow-moving parking lot has a different job than one facing a busy road. Drivers traveling at higher speeds have less time to find, read, and understand a sign. The height of the building, distance from the street, angle of traffic, nearby trees, and other signs in the area can all affect visibility. We look at the chart, and we also look at how people will actually approach the property.

Every city has its own sign code, and the amount of signage allowed on a building is often based on things like tenant frontage. A landlord or shopping center may have another set of requirements. Those rules may cover the location, maximum letter height, colors, lighting, and mounting method.

One of our goals when designing commercial building signs is to make the best use of the space the city and property allow. And that’s where things can get interesting. Let’s say you’re opening a dental office and your business has a long name. Putting the entire name from your business card on the building might sound like the obvious choice.

Once everything is reduced to fit the allowable sign area, the letters may end up too small to be useful from the road. Sometimes a large, easy-to-read DENTIST is going to do a much better job than a long business name squeezed onto the building in smaller letters.

Your building sign and your business card don’t necessarily have to do the same job. A business card can include your full name, logo, tagline, phone number, website, and a list of services. Someone holding the card has time to look at all of it. Your building sign has a much shorter window to communicate with someone, especially when that person is driving by.

We start by asking what customers need to see first. Is it the business name? A recognizable logo? A simple description of the service? The answer depends on the business and the location. For a well-known company, the logo may be enough. A newer business may need a short description that helps people understand what it does.

Letter height is only part of the picture. Thin lettering can disappear from a distance. Decorative fonts may become difficult to read when they’re mounted high on a building. Letters placed too close together can run into each other visually, especially at night.

Color contrast also affects readability. Dark letters may disappear against a dark wall. Light letters can get lost against a pale background. The lighting method and wall material can change how the sign looks after sunset.

That’s why we review letter size, spacing, font style, color, wall surface, and illumination when designing channel letter signs. Sometimes your full logo works well exactly as designed. Other times, simplifying part of it produces a much better building sign.

We don’t stop after confirming that a design technically fits within the allowable sign area. We think about the available space, viewing distance, traffic speed, letter size, contrast, landscaping, and what you need people to see. We also consider how the sign will look during the day and at night.

After all, a beautiful sign doesn’t help much if nobody can read it. The best sign makes good use of the space you have and helps your customers find you.

At Bootz & Duke, we’ve been designing and building commercial signs in Arizona since 1964. If you’re trying to determine the right letter size for a new storefront or building sign, contact Bootz & Duke or request a free quote. We’ll look at the property, viewing distance, sign code, and design before recommending a size.