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Ken Ward's Writing Pages
Writing: Using Readability WriteItRead Rudolph Flesch

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The Flesch Reading Ease Formula and the Flesch-Kincaid Formula both use the Average Number of Words Per Sentence (Average Sentence Length) and Average Number of Syllables Per Word (Average Syllables per Word) as measures of readability.

Flesch Reading Ease

The Flesch Reading Ease Formula is:
Where ASL is the average sentence length (in words), and ASW is the average syllables per word. Alternatively, it can be written more clearly as:

The Flesch Reading Ease score is interpreted as follows:
Flesch Reading Ease Score Readability LevelEducation LevelPercentage Adults (Optimistic)
0 - 29 Very difficultCollege Graduates5%
30 - 49 DifficultCollege30%
50 - 59 Fairly difficultSenior High School, A-level50%
60 - 69 Plain English13 to 15 year-olds80%
70 - 79 Fairly easy12 year-olds90%
80 - 89 Easy11 year-olds.
90 - 100 Very easy10 year-olds
We can take the Flesch Reading Ease score to indicate roughly the percentage of the population able to read writing at this level. However, the above table is likely to be more appropriate to the population of the USA in the 1950's. See British American Comparison for equivalents to USA Grades.

Flesch-Kincaid Grade Level

The Flesch-Kincaid Grade Level Formula is:
Where ASL is the average sentence length in words, and ASW is the average syllable length of words (as above). A clearer version is:

The Flesch-Kincaid Grade Level uses USA Grades a comparison with the British system is here.

Sentence Length and Syllables per Word

GradeSyllables/wordAverage Sentence Length
College/University1.8519 (14-23)


PublicationReading EaseASLASW

Ken Ward's Writing Pages

The Last Place in Space
- by Ken Ward

When pilot Philip Turner is accidentally transported by an anomaly and marooned on an unknown planet, he discovers the planet is threatened by a group of ruthless aliens similarly marooned. With the help of a group of young women with superpowers, and a powerful being called a god, he reluctantly uses his advanced knowledge and technology to help the planet's inhabitants, but will he succeed when outnumbered by aliens, opposed by greedy and squabbling kings, and limited by his gentle nature and moral beliefs? Paperback and Kindle:
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The Last Place in Space