dale-chall-formula

Formula to detect the grade level of text according to the (revised) Dale–Chall readability formula.

See dale-chall for a list of words which count as “familiar”.

Install

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

npm:

npm install dale-chall-formula

Use

import {daleChallFormula, daleChallGradeLevel} from 'dale-chall-formula'

daleChallFormula({word: 30, sentence: 2, difficultWord: 6}) // => 4.41208

daleChallFormula({word: 30, sentence: 2}) // => 0.744

daleChallFormula() // => NaN

daleChallGradeLevel(daleChallFormula(30, 2, 6)) // => [9, 10]

API

This package exports the following identifiers: daleChallFormula, daleChallGradeLevel. There is no default export.

daleChallFormula(counts)

Given the number of words (word), the number of sentences (sentence), and the number of unique unfamiliar words in a document (difficultWord), returns the score associated with the document.

daleChallGradeLevel(score)

Given a score, returns the corresponding grade ranges

Score	Corresponding Grade Level	Return value
Less than 5	Grade 4 and lower	[0, 4]
Less than 6	Grades 5 and 6	[5, 6]
Less than 7	Grades 7 and 8	[7, 8]
Less than 8	Grades 9 and 10	[9, 10]
Less than 9	Grades 11 and 12	[11, 12]
Less than 10	Grades 13 and 15 (College)	[13, 15]
Higher	Grades 16 and higher (College Graduate)	[16, Infinity]

Related

• automated-readability — Uses character count instead of error-prone syllable parser
• coleman-liau — Uses letter count instead of an error-prone syllable parser
• flesch — Uses syllable count
• flesch-kincaid — Like flesch-formula, 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