Readability Checker — Flesch, Grade Level & Hard Sentence Finder
Score your text with Flesch, Flesch–Kincaid, Gunning Fog, SMOG and more, and see the long sentences and hard words to fix.
English only. Paste plain text; headings and list items on their own line count as separate sentences.
The report was written by the team in a single afternoon. It was reviewed carefully and was approved quickly. Simple words help: use "use" instead of "utilize" and "help" instead of "facilitate".
Long = 20 to 29 words, very long = 30 or more. Hard words have three or more syllables (not counting names, hyphenated compounds, or an -es, -ed or -ing ending). Passive voice is detected by pattern (“was written”), so check each one; some are fine.
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This free readability checker scores your text with the six standard formulas, Flesch Reading Ease, Flesch–Kincaid Grade Level, Gunning Fog, SMOG, Coleman–Liau and the Automated Readability Index, and then shows you where the difficulty is. Long sentences are shaded, words of three or more syllables are underlined, and likely passive voice and -ly adverbs are marked, so a score of 45 comes with a list of the sentences that caused it.
Every formula measures the same two things: how long the sentences are and how long the words are. They know nothing about meaning, order or jargon, so a short sentence full of obscure terms can score as easy, and a score is a prompt to look, not a verdict. Used that way they are useful: if your average sentence runs past 25 words, or a third of your words have three syllables, readers will feel it. The checker is designed for English; the formulas do not apply to other languages.
How to use
- Paste your text. Headings and list items on their own line count as separate sentences.
- Read the Flesch Reading Ease score (higher is easier; 60 to 70 is plain English) and the grade levels (lower is easier).
- Look at the highlighted copy. Yellow sentences have 20 to 29 words, red ones 30 or more. Split them first; it is the fastest gain.
- Replace underlined hard words where a shorter word says the same thing, and check each passive-voice and adverb mark.
- Edit in the box above and watch the scores update.
Frequently asked questions
What is a good Flesch Reading Ease score?
For text aimed at the general public, 60 to 70 is the usual target; Flesch called this range plain English, readable by 13- to 15-year-olds. 70 and above is easy, typical of popular fiction. 30 to 50 is difficult, typical of academic and legal writing, and below 30 is very difficult. Technical audiences tolerate lower scores, but nobody prefers them.
What is the difference between Flesch Reading Ease and Flesch–Kincaid Grade Level?
They use the same inputs, words per sentence and syllables per word, weighted differently. Reading Ease gives a score where higher means easier, roughly 0 to 100. The Flesch–Kincaid Grade Level, developed for the US Navy in 1975, converts the same measures into a US school grade, so 8.0 means an eighth grader should understand it.
What grade level should I write at?
For a general audience, aim for grade 8 or below. Health-literacy guidance from bodies such as the US National Institutes of Health and the American Medical Association recommends patient materials at a 6th to 8th grade level. Most well-edited newspapers and websites land between grades 8 and 11. A lower grade is not dumbing down: specialists read plain text faster too.
Why do the formulas give different grade levels?
Each formula was fitted to a different set of test texts and readers and counts slightly different things. Gunning Fog and SMOG count words of three or more syllables, Coleman–Liau and ARI count letters instead of syllables, and Flesch–Kincaid uses the average syllables per word. Expect a spread of two or three grades; the average is a reasonable single figure.
How accurate is the syllable count?
English spelling does not map neatly to sound, so every automatic counter makes mistakes. This one uses rules for silent e, plurals, -ed endings, syllabic -le (ta-ble) and common vowel pairs, plus a list of irregular words, and is tested against more than 150 words with known counts. On ordinary prose an occasional miscount moves the scores by a fraction of a point.
Is passive voice always wrong?
No. Passive voice is the right choice when the actor is unknown or unimportant (“the bridge was built in 1932”). It becomes a problem when it hides who is responsible or makes sentences longer. The checker finds passives by pattern, a form of be or get followed by a past participle, so it also flags some adjectives (“was tired”). Treat each mark as a question.
The six formulas
• Flesch Reading Ease (1948): 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Higher is easier.
• Flesch–Kincaid Grade Level (1975): 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. Developed for US Navy training manuals.
• Gunning Fog Index (1952): 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]. Complex words have three or more syllables, not counting proper nouns, hyphenated compounds, or a third syllable that comes only from -es, -ed or -ing.
• SMOG (1969): 1.043 × √(polysyllables × 30 ÷ sentences) + 3.1291. Designed for samples of 30 sentences; on shorter texts treat it as rough.
• Coleman–Liau Index (1975): 0.0588 × L − 0.296 × S − 15.8, where L is letters per 100 words and S is sentences per 100 words. Built to be computed without counting syllables.
• Automated Readability Index (1967): 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43. Designed for the US Air Force to be computed from character counts.
Flesch Reading Ease score table
• 90–100: very easy, understood by an average 11-year-old (5th grade).
• 80–90: easy (6th grade). 70–80: fairly easy (7th grade).
• 60–70: plain English, 13 to 15-year-olds (8th and 9th grade).
• 50–60: fairly difficult (10th to 12th grade).
• 30–50: difficult (college level).
• 0–30: very difficult (college graduate). Most legal contracts and many academic papers score here.
What actually moves the score
Sentence length is the biggest lever. Splitting one 40-word sentence into two of 20 changes Flesch–Kincaid by several grades for that passage, and it nearly always helps readers too. Start with the red sentences, then the yellow ones.
Word length is the second lever. Swap long words for short ones where the meaning is the same: use for utilize, help for facilitate, about for approximately, start for commence. Do not swap technical terms your readers need; a doctor writing for doctors should say myocardial infarction. And do not chase the number by chopping every sentence to five words, which produces text that scores well and reads like a telegram.
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