Readability of a text

How to use the tool

Paste your text into the field: the score updates as you type. For an article that is already published, enter its address instead and click “Fetch”: the tool reads the page, isolates its main content and puts it in the field, where you can still edit it. A drop-down switches between the main content and the whole page.

The language of a pasted text is detected, and you can change it in the list. It selects the formula: English or French. Sentences whose length reaches the threshold set under the result are highlighted in the text, with their word count on hover.

The formulas used

The Flesch score (Flesch Reading Ease) comes from a 1948 article by Rudolf Flesch in the Journal of Applied Psychology. It combines two measures: the average sentence length in words and the average word length in syllables.¹ The higher the score, the easier the text is to read.

Formulas quoted from Bendová (2021).¹

The constants depend on the language: a French word has more syllables on average than an English one, so the original formula would unfairly penalise a French text. Kandel and Moles published their adaptation in 1958 in the Cahiers d’études de radio-télévision.¹ The score can fall outside the 0 to 100 range: a text with very long sentences and very long words gives a negative number.

Reading the score

In his book The Art of Readable Writing, Flesch proposes a grid that matches each score band to a difficulty level.¹² The tool uses this grid for English and applies it to French as well, as a choice: no grid specific to French was read for this page.

A low score does not flag a bad text. A legal notice or a technical sheet will be difficult for good reasons, and a text for the general public benefits from aiming higher. The score is mostly useful to compare two versions of the same text and to spot passages to lighten.

How the tool counts words, sentences and syllables

A word is a run of characters between two blanks that contains a letter, as in the word counter. “Don’t” and “well-known” each count as one word, and a lone number is ignored. Sentences are split by the browser, and each line also ends a sentence: a heading or a bullet without a final full stop therefore counts as a short sentence.

The syllable has no single mechanical definition, especially in French. The tool applies these rules for French:

• each group of vowels counts as one syllable (“maison”: 2);
• a silent final e is removed after a consonant or after an é (“table”: 1, “année”: 2);
• “qu” and “gu” before e, i or y count without the u (“longue”: 1);
• a diaeresis, or an é followed by a vowel, splits two syllables (“aïeul”: 2, “créé”: 2);
• words with an apostrophe or a hyphen are counted piece by piece (“aujourd’hui”: 3).

An inner e and the ending “-ent” count as syllables, which slightly overestimates some words (“référencement”: 5, “parlent”: 2). For English, the tool counts groups of one or two vowels, removes final -e, -es and -ed, and counts one syllable for any word of three letters or fewer.

Readability and SEO

Google publishes no readability score to reach. I found none in its documentation on creating helpful content.⁴ John Mueller, who speaks for Google, said in a 2018 question session that it is probably not something to focus on from an SEO point of view, and that Google does not use a simple word count to determine a reading level.³

Readability matters for another reason: a reader who stumbles on endless sentences leaves. The tool helps you write for your audience. To measure the length of a text, use the word and character counter, and to check that a keyword is not overused, the keyword density analysis. On a text produced with AI, readability is part of the review before publication.

Limits of the score

The score only looks at sentence and word length. It understands neither meaning nor structure: a text with short but incoherent sentences gets an excellent score. It also ignores headings, lists, examples and layout, which matter to the reader.

Syllable counting in French is approximate. The author of the study cited above notes that its complexity may explain poorer results for French than for other languages.¹ Compare scores obtained with the same tool, and look at the gap between two versions rather than the absolute value. The reading is done on the HTML returned by the server: a page that only shows its text with JavaScript will return little text, so paste it by hand.

Frequently asked questions