WP Readability Analysis is a wordpress plugin that calculates the index
of readability of a post or page using various methods: Gulpease, Gunning-Fog,
Flesch and Flesch-Kincaid.
With these formulas we try to analyze how difficult it is to read a text.

The method Gulpease, calibrated for the Italian language, unlike the other
is based on word length in letters rather than syllables.

Methods Flesch-Kincaid and Flesch, who are the most famous, using formulas based
on the average number of words per sentence and the average number of syllables per word.

The method Gunning-Fog uses a formula based on the average number of words per
sentence and the percentage of words with 3 or more syllables.

Unlike Gulpease, these three methods are mainly used in the English language.
Both Gunning-Fog that Flesch-Kincaid return a score which is the number of
years of education that the user must have to understand the text.

I invite you to know more about the various pages of wikipedia devoted
to the various formulas.