What is readability?

Reading any text shouldn’t require any extra effort from the reader beyond being able to actually read; words and sentences should be immediately comprehensible. Readability then is the ease with which a reader can understand a written text.

The total sum of elements within a given piece of written text that affect the success of a group of readers has with it. The success is the extent to which they understand it and read it at an optimal speed.

There is where design skills come into play, the challenge is to ensure that the words, sentences, and paragraphs are arranged in groups of words that are given their best chances to jump out of the page.

The responsibility for good readability falls to the designer.

We don’t tend to read individual words; we read using saccadic movements, which means we take in familiar groups of words using rapid eye movements.

Think about the intended use

Achieving a high level of readability doesn’t necessarily require the presence of a highly-legible font.

The common mistake is an inappropriate typeface choice. Some typefaces are designed specifically for text setting, some for display and some for signage.

Using the wrong kind of font doesn’t indicate a bad typeface design; it indicates a bad typeface choice.

Take some time to find out the background of a typeface design before using it in a project and always remember that a font that woks well at larger designs, like a poster, isn’t necessarily going to work in smaller pieces like an article.

Character count per line

The other dominant factor affecting readability is character-count-per-line. Including spaces, an idea count is reckoned to be somewhere between 50 and 75.

If a measure (the length of a line of text) becomes too long, the readers’ eyes struggle to locate the start of the next line in a paragraph.

If it is too short, the reading experience becomes too jerky and loses rhythm.

So, for example, novels require a relaxed rhythm while newspaper columns can be set over a shorter measure because the text is verbally broken into shorter snippets of information.

In the following examples at just over 50 characters per line, the first example scans comfortably from line to line.


In the second example, a wider measure of over 120 characters becomes much harder to locate the start of each subsequent line, creating bad readability.

readability 120

Optimal line length in web design

In web design, you can achieve an optimal number of characters per line by restricting the width of your text blocks using em or pixels.

Regardless of which one you choose, your layout will have to be in a fixed-width if you want to achieve an optimal line length for the majority of your visitors.

You should have around 60 characters per line if you want a good reading experience.

In mobile devices you should go for 30–40 characters per line.

What is a readability score?

Readability scoring approximates how many years of schooling someone needs to be able to understand your writing.

For example, a Flesch-Kincaid readability score of around 8 is roughly equivalent to a reading level of US grade 8 – ages 13-14.

When text is too difficult or awkward to read, messages may not be engaged with or understood. On the flip side, when writing is too simplistic, your audience might feel patronized or just plain bored.

How to test your text readability

There are some readability tools on line a very good one is:


You can test webpage readability or input your own text.

test your text readability

This article is the first on a series of articles where we will be covering principles of good typographic design, like cases, contrast and color.

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Javier Cantero

Javier Cantero