At first glance, the formulas for the readability scores may not seem to make sense. But, the building bricks that make up both Flesch scores are straightforward and based on two factors:
- Sentence length. As judged by the average number of words in a sentence
- Word length. As judged by the average number of syllables in a word
Sentences that contain a lot of words are more difficult to follow than shorter sentences.
Many of the classics of English Literature were written in the 18th and 19th centuries. During this time, the average sentence was a lot longer than it is now.
You could have a long paragraph which was one long sentence; strings of clauses connected with peppered semicolons were the norm. However, because the average length of a sentence has decreased with time, so has our attention span. We no longer have the tolerance for lengthy, meandering prose.
Similarly, words that contain a lot of syllables are harder to read than words that use fewer syllables. For example, “it was a lackadaisical attempt” is more difficult to read than “it was a lazy attempt”.
What do the Flesch scores mean?
Both Flesch scores reflect how readable a piece of content is. The Flesch Reading Ease score is between 1 and 100, and the Flesch Kincaid Grade Level reflects the US education system. They are both calculated with the same units, but the weightings for these units are different between the two tests, resulting in different readability scores.
Flesch-Kincaid Reading Ease
The higher the reading score, the easier a piece of text is to read.
Note that this differs from the majority of readability scores where a lower score is easier.
For example, a reading score of 60 to 70 is equivalent to a grade level of 8-9 so a text with this score should be understood by 13 to 15-year-olds.
To make sense of a Reading Ease score, a conversion table is needed. This translates the score into a grade level.
Flesch-Kincaid Grade Level
The Flesch-Kincaid Grade Level is equivalent to the US grade level of education. It shows the required education to be able to understand a text.