Check readability. Six formulas, one plain score.

How a readability checker works

Readability formulas do not understand meaning. They count things: sentences, words, syllables, letters. Long sentences and long words make text harder to read, so each formula turns those counts into a number. That is both their strength (they are fast, consistent and published) and their limit (a short, clear sentence of nonsense scores well). This readability checker runs six published formulas side by side, then adds checks the formulas miss, such as passive voice and paragraph length.

The six formulas, and where they come from

• Flesch Reading Ease. 206.835 - 1.015 × (words per sentence) - 84.6 × (syllables per word). Rudolf Flesch, 1948. Higher is easier.

• Flesch-Kincaid Grade Level. 0.39 × (words per sentence) + 11.8 × (syllables per word) - 15.59. Developed for the US Navy in 1975 by J. Peter Kincaid and his team. The result is a US school grade.

• Gunning Fog. 0.4 × (words per sentence + 100 × share of complex words), where a complex word has three or more syllables. Robert Gunning, 1952.

• SMOG. 1.0430 × √(polysyllables × 30 / sentences) + 3.1291. G. Harry McLaughlin, 1969. It was normed on 30-sentence samples, so we only show it once your text reaches 30 sentences.

• Coleman-Liau. 0.0588 × L - 0.296 × S - 15.8, where L is letters per 100 words and S is sentences per 100 words. Meri Coleman and T. L. Liau, 1975. It counts letters, not syllables.

• Automated Readability Index. 4.71 × (characters per word) + 0.5 × (words per sentence) - 21.43. R. J. Senter and E. A. Smith, 1967.

The formulas disagree by a grade or two on the same text because they weigh different things. That is normal. We show each one and score the median, so no single formula decides your result.

What is a good Flesch Reading Ease score?

On Flesch's scale, 60 to 70 maps to an 8th or 9th grade reading level, 50 to 60 to 10th to 12th grade, and 30 to 50 to college. The scale is used well beyond classrooms: the US Department of Defense uses it as the standard readability test for its documents, and Florida requires insurance policies to score 45 or higher. For posts, emails and web pages we aim for 60 or above. The Gunning Fog index has a similar rule of thumb: text for a wide audience generally needs a score under 12.

The seven checks behind the score

• Flesch Reading Ease, 25 points. Pass at 60 or above.

• Grade level, 15 points. The median of the grade formulas. Pass at grade 9 or below.

• Long sentences, 20 points. GOV.UK's guidance is to split sentences over 25 words. We highlight each one.

• Paragraph length, 10 points. GOV.UK also caps paragraphs at 5 sentences.

• Passive voice, 10 points. US government plain language guidance says passive voice hides who does what.

• Plain words, 10 points. “Buy” not “purchase”, “help” not “assist”, “about” not “approximately”.

• Rhythm, 10 points. Sentences that are all the same length read flat, even when they are short.

Easy to read is the floor. Sounding like you is the point.

A clean score means people can follow you. It does not mean they will remember you. Content that reads easily and still sounds like one specific person is the harder part, and that is what VoiceMoat is built for. audenAI, the brain inside VoiceMoat, learns your voice from your own content and drafts posts that are clear and recognizably yours, and Voice Lab shows you what that voice is made of. Check your title with the headline analyzer, scan for AI patterns with the AI detector, and if a draft reads machine-made, humanize AI text rewrites it.