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Readability Scores

According to the Center for Plain Language, "Readability is about making your digital content clear and easy to understand. When you focus on readability, you increase the chance your target audience will actually read and interact with your content. For this reason, readability should be a natural part of your content management."

Readability formulas usually look at factors like sentence length, syllable density and word familiarity as part of their calculations. The formula may also include complexity, familiarity, legibility and typography.

Readability vs. Legibility

vanseo design describes the difference between legibility and readability like this:

  • "Legibility – a measure of how easy it is to distinguish one letter from another in a given typeface. Legibility describes the design of a typeface. How legible a typeface is designed to be depends on its purpose. Legible typefaces usually have larger closed or open inner spaces (counters). They generally have a larger x-height, though not too large."

  • "Readability – how easy words, phrases, and blocks of text can be read. Readability describes how a typeface is used on the page. Good typography (more readable) encourages a desire to read the copy and reduces the effort required to read and comprehend the type. The reader shouldn't even notice the type. She should simply understand the words."

Why Should I Be Concerned About Readability?

  • It influences how clearly a text can be understood by the reader.
  • It allows your text to match your audience better.
  • It improves reader engagement with online text on web pages, social media, and all other digital and printed marketing materials.
  • when writing instructional or "how-to" information / manuals.

Readability Scores

In 1921, Edward Thorndike published a book called "The Teacher's Word Book." In this book, he researches the frequency of "difficult words" found in literature. This was the first time a formula was applied to language.

What's in a score?

Readability scores are created by collecting key metrics that are related to text and then plugging that data into a specific mathematical formula(s) to calculate.

As mentioned above, some of the metrics included in a readability score are sentence length, syllable density and word familiarity as well as complexity, familiarity, legibility and typography.

Not all readability score formulas use the same metrics. For example, the Flesch readability formulas (Reading Ease and Kincaid Grade Level) use sentence length, determined by the average number of words in a sentence, and word length, which is calculated by the average number of syllables in a word. Gunning Fog, which estimates the grade level required to comprehend the text, also uses sentence length, but instead of word length, it calculates "difficult words," which are words that are three or more syllables.

As important as readability scores are in helping to improve text accessibility for all your users, there are a few drawbacks to keep in mind:
  • Readability scores do not provide information on the actual quality of the text. Is it grammatically correct and appropriate for the audience? Are there spelling errors?
  • They are not very useful with microcopy or small snippets of text. If you analyze just a small portion of your text, you are not getting the "whole picture."
  • Since formulas differ in the use of metrics, it's a good idea to use several different scores all together.
  • A low score doesn't always mean better readability. For example, text written for scientific purposes will have a higher readability score than text written for a children’s book.

What is a good score?

A good readability score should match your target audience(s). Review the different tests and what they measure. Determine the criteria that are important to your target audience and then choose several formulas that measure those criteria.

Don't forget! Readability scores are just one influencing factor on the total quality of your text and the users'experience. Spell check, thoughtful typography choices and appropriate grammar are equally important in creating text that is useful, usable, accessible and understandable.

Make sure you check out our help doc titled "What is Readability? Why does it matter?" for more detailed information about the six popular readability tests DubBot uses.


Maggie Vaughan, CPACC
Content Marketing Practitioner