Writing - Written by on Tuesday, October 23, 2012 10:55 - 0 Comments

Determine Readability Using the Flesch Reading Ease

A concern of any good author is the readability of his/her text, with primary consideration given to intended audience. If readability is too low, the author risks the esoteric; if too high, the mundane. A method of calculating readability objectively allows not only evaluation of a single manuscript, but also the ability to compare multiple manuscripts using a definite scale.

Rudolf Flesch developed the Flesch Reading Ease Test in the mid-20th century to fill this need, but the formula is both complicated and based on Flesch’s assumptions. The test is included in several word processing programs and continues to be used frequently even though its derivation is largely unknown to users.

Background of the Flesch Reading Ease

Rudolf Flesch (1911-1986) was an author and writing consultant remembered most for his 1955 book Why Johnny Can’t Read. Raised in Austria, he studied law and later moved to the United States, earning a PhD from Columbia University. The author of many books on teaching English, he established himself as an expert in the field. In a 1949 book titled The Art of Readable English, he introduced a formula for calculating readability. The formula, which relies on statistics published by another author, is based on the trend of decreasing sentence length since the 16th century.

Flesch Reading Ease Formula

The Flesch Reading Ease Test is calculated by the following method: Average sentence length is multiplied by 1.015, and average number of syllables is multiplied by 84.6. These two products are subtracted, and the difference is subtracted from 206.835, resulting in a score ranging from 0 to 100. Therefore, the formula is:

206.835 – 1.015 (total words/total sentences) – 84.6 (total syllables/total words)

A score of 100 represents the easiest to read text and a score of 0 represents the most difficult to read text. Scores from 60 to 70 are plain English, readable by the average literate reader.

Flesch-Kincaid Grade Level Formula

To translate the Flesch Reading Ease Test to a grade level, the Flesch-Kincaid formula is useful. The formula takes average sentence length and multiplies it by 0.39, and average number of syllables and multiplies it by 11.8. These products are summed, and the result is reduced by 15.59. Therefore, the formula is:

0.39 (total words/total sentences) + 11.8 (total syllables/total words) – 15.59

A score of about 65 correlates with the 8th to 9th grade level, and a score of about 55 indicates a 10th to 12th grade level. Scores between 0 and 30 represent college graduate readability.

A competing readability scale developed by Robert Gunning called the Fog index considers the percentage of foggy words or words with 3 syllables or more. Otherwise, the index is similar in purpose to the Flesch method.

A Problem with Readability Formulae

A problem with readability formulae is they ignore vocabulary. For example, the words governmental and acephalous both have 4 syllables and contribute to the syllable portion of the Flesch Readability statistic equally. However, governmental contains 12 letters thereby contributing to a lower score than the 10 letters in acephalous. The problem is that the test assumes a strong negative correlation between word length and readability. Clearly, acephalous appears rarely in written (or spoken) English, whereas governmental is much more common.

Readability statistics provide a quick solution to evaluating audiences most likely to be able to read a manuscript, but there are some caveats. An ideal scale considers more than just calculations of words and syllables, and authors must consider the lexicon used in manuscripts. For a one-click evaluation, the Flesch Reading Ease provides a glimpse of readability, but every good author knows not to rely on this method exclusively.

Comments are closed.

Author Information

John GargerJohn Garger is a copy editor, proofreader, dissertation coach, researcher, writer, and entrepreneur living in upstate New York, USA.

RSS FeedYouTubeFacebookJohn Garger at LinkedIn


CoachingCopy EditingProofreadingMock Journal Review

Writing - Oct 23, 2012 10:55 - 0 Comments

Determine Readability Using the Flesch Reading Ease

More In Writing

Dissertations - Jun 19, 2011 5:37 - 0 Comments

Tips for Getting Started on a Dissertation

More In Dissertations

Methodology - Jan 10, 2011 9:17 - 0 Comments

Latent Constructs in Social Science Research

More In Methodology