flesch

Formula to detect the grade level of text according to the Flesch reading ease.

See syllable for detecting syllables.

Install

This package is ESM only: Node 12+ is needed to use it and it must be imported instead of required.

npm:

npm install flesch

Use

import {flesch} from 'flesch'

// For “The cat sat on the mat” (1 sentence, 6 words, 6 syllables).
flesch({sentence: 1, word: 6, syllable: 6}) // => 116.14500...

// For “The Australian platypus is seemingly a hybrid of mammal and reptilian
// creature.” (1 sentence, 12 words, 23 syllables).
flesch({sentence: 1, word: 12, syllable: 23}) // => 32.50499...

API

This package exports the following identifiers: flesch. There is no default export.

flesch(counts)

Given an object containing the number of words (word), the number of sentences (sentence), and the number of syllables (syllable) in a document, returns the reading ease associated with the document.

Returned values are 120 (every sentence consisting of only two one-syllable words), or lower (including negative values).

The values have the following semantics:

Score	Semantics
90.0 – 100.0	Easily understood by an average 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

Therefore we can use the following formula to approximate the average age a student would understand a document at, given score score:

var age = 20 - Math.floor(score / 10)

Related

• automated-readability — Uses character count instead of error-prone syllable parser
• coleman-liau — Uses letter count instead of an error-prone syllable parser
• dale-chall-formula — Uses a dictionary, suited for higher reading levels
• flesch-kincaid — Like flesch, returns U.S. grade levels
• gunning-fog — Uses syllable count, needs POS-tagging and NER
• smog-formula — Like gunning-fog-index, without needing advanced NLP
• spache-formula — Uses a dictionary, suited for lower reading levels

License

MIT © Titus Wormer