Have you ever been driving down the highway and looked at a billboard and thought, “What a ridiculous billboard! Great picture…but I have absolutely no idea what it says!”? Because the type face is so small that no one but someone who climbed up on the billboard itself could possibly read it! You definitely don’t want that happening to your sign. So how do you know what the right size is? Keep in mind that you also want to maximize the space on the sign that you have and get as much information in as is reasonable in the space available. Well…within reason.
The rule of thumb is pretty easy for optimum viewing: 1” of letter height provides 10 feet of readability. So 3” of letter height can be read (optimally) from 30 feet. 24” letter height can optimally be read from 240 feet. Even for the many of us for whom math class was a bitter struggle, the formula for optimum viewing is pretty easy to grasp. However, remember that this is for optimum viewing, not the absolute maximum distance from which they can be seen.
See the chart here for a more detailed view, but keep in mind that this also depends on an individual’s eyesight as well.
|Letter Height (inches)||Distance for Best Impact (feet)||Max Readable Distance (feet)|
Factors beyond size
Aside from the size, there are other considerations that make a sign easier or more challenging to read. Color has a significant impact as well. There is an actual scientific theory based on Johann Wolfgang von Goethe’s theory of color contrast which gives a precise scientific calculation for determining the ratio of contrast of two colors. I will save you the mathematics, but suffice it to say that the very best color combinations are a white background with black, blue or red font; a black background with white or yellow font; or a yellow background with black, red or blue font.
You can see here the fonts that do and don’t work as well – and again, I’ll save you the actual mathematic formula, but suffice to say that the higher the number, the better the contrast and greater the readability, the lower the number, as you can easily see, the harder it is to read.
If the background color is similar to the font color, it can be difficult to read at any distance.
Font is another contributor to the ease of readability. A bolder font is easier to read than one that has thinner lines. Script fonts are harder to read than straight, upright fonts. Having enough spacing between letters (kerning) also makes a difference. This may all seem obvious when you think about it, but it’s remarkable how many people lose sight of these facts when they put up their signs. People sacrifice a lot in the name of style and aesthetics. Style and aesthetics are important, but remember, if nobody can read thedarn thing, they won’t matter at all.