Readability is the ease in which text can be read and understood, as in the quality of written language. This should not be confused with ‘legibility’ which is a measure of how easily individual letters or characters can be distinguished from each other. An article can be perfectly legible but difficult to read (poor readability) and genuinely well written but illegible (Jane Austen in green text over blue background). Here, I’m talking about readability.
Researchers and linguists have devised various formulas to test the readability of a piece of text. One of the oldest and most accurate readability formulas was developed by Rudolph Flesch, an author, writing consultant, and a supporter of the Plain English Movement, in 1948. The Flesch Reading Ease Formula is a simple approach that measures how easy a text is to read by taking into account just two factors - the average length of a sentence and the average number of syllables per word.
Flesch's work made an enormous impact on journalism, when publishers discovered that the Flesch formulas could increase readership up to 60 percent. Soon it became one of the most widely used readability formulas.
The Flesch Reading Ease Scale ranges from 0 to 100. The higher the rating, the easier the text is to understand. The scores of this scale can be interpreted as following:
- 90.0 - 100.0: Easily understandable by 11 year old student
- 60.0 - 70.0: Easily understood by 13- to 15-year-old students
- 0.0 - 30.0: best understood by university graduates
For example, Reader's Digest magazine has a readability index of about 65, Time magazine scores about 52, and the Harvard Law Review has a readability score in the low 30s.
In 1975, in a project sponsored by the U.S. Navy, the Flesch Reading Ease formula was recalculated to give a grade-level score and the new formula was called the Flesch–Kincaid Grade-Level formula.
The Flesch–Kincaid Grade Level Formula translates the 0–100 score to a U.S. grade level, making it easier for teachers, parents, librarians, and others to judge the readability level of various books and texts. A grade level of 9.9 means that the text is easily understood by 9th to 10th grade students.
Calculate Readability Score in Microsoft Word
Most users are not aware that they can calculate both Flesch Reading Ease Score and Flesch–Kincaid Grade Level in Microsoft Word, mainly because this particular tool is disabled by default.
To enable readability statistics open Microsoft Word 2007 or 2010, click on File and choose Options.
Click on Proofing on the left side and place a checkmark in the box next to ‘Show readability statistics’.
Close all dialog boxes and return to your document. Press F7 or from the Review tab click on the Spelling and Grammar button. This will bring up the spell check wizard. Allow the wizard to complete the spell check, at the end of which the readability statistics will be revealed.
As you can see, the readability statistics display the total number of words, characters, paragraphs and sentences, various averages for sentence, word and character, percentage of passive sentences and lastly, Flesch Reading Ease and Flesch–Kincaid Grade Level scores.
Aside from spell and grammar checks, you can use the Flesch score to determine whether the type of documentation you are working on can be comfortably read and understood by your target audience, and if not, strive to achieve a reasonable score.