Readability Checker

How to Use the Readability Checker

Paste your text into the box, or type straight into it. The scores update as you type, and the copy of your text under the results shows three kinds of marks: yellow for sentences over 25 words, blue for passive voice candidates and purple for adverbs ending in -ly. Click a long sentence in the list to jump to it in the marked-up copy.

The checker runs entirely in your browser. Your text is never uploaded, saved or sent anywhere, so it is safe to paste an unpublished chapter. It handles a whole chapter of 10,000 words or more without slowing down.

Give it enough text to judge. On a short passage, one long sentence can move the score by several points, so a full scene or chapter tells you more than a few lines. Paste plain text if you can: a heading or a list item without a full stop counts as a sentence of its own, which nudges the score up.

What Your Readability Score Means

The Flesch Reading Ease score runs roughly from 0 to 100. The higher the number, the easier the text. Rudolf Flesch tied each band of the scale to a school grade, and the checker uses his bands for its verdict:

The Flesch-Kincaid Grade Level reads the other way: it names the US school grade that should manage the text, so a lower number is easier. Both scores are built from the same two measurements, which is why they nearly always move together.

The scale is open at both ends. A page of very short words in very short sentences can score above 100, and dense academic prose can fall below zero. This sentence scores about −90 in the checker: Utilization of comprehensive promotional methodologies facilitates considerable improvement in the visibility of independently published literature. Said plainly, as Good marketing helps more readers find a self-published book, it scores 66, in the plain-English band.

Flesch Reading Ease Calculator: The Formula

Rudolf Flesch published the formula in 1948, in a paper called “A New Readability Yardstick” in the Journal of Applied Psychology. It needs three counts: words, sentences and syllables.

Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)

The example text in the box shows how it works. It has 103 words in 7 sentences, with 130 syllables. That gives 14.71 words per sentence and 1.262 syllables per word:

206.835 − (1.015 × 14.71) − (84.6 × 1.262) = 206.835 − 14.93 − 106.78 = 85.1

The weights show where the points go. Each extra word in the average sentence costs about one point. Each extra syllable in the average word costs 84.6 points, so a rise from 1.3 to 1.4 syllables per word costs about 8.5 points, as much as adding eight words to every sentence.

Flesch-Kincaid Grade Level

In 1975 J. Peter Kincaid and his colleagues adapted Flesch's measurements for the US Navy, so that the result came out as a school grade instead of a 0 to 100 score:

Grade Level = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59

On the same example text: 0.39 × 14.71 + 11.8 × 1.262 − 15.59 = 5.0, a fifth-grade level. Microsoft Word shows both scores in its readability statistics, so many writers have seen them already. They also turn up in law: Florida's statute on readable insurance policies (section 627.4145) asks for a Flesch Reading Ease score of at least 45.

How the Checker Counts Syllables

Syllables are the hard part. The checker has no dictionary; it counts groups of vowels and then corrects them with the rules of English spelling: a silent e at the end (make), the silent e in -ed and -es endings (jumped, lives), which is sounded after t or d (wanted) and after s, x, ch or sh (boxes), the extra syllable in -le (ta-ble) and in -ing after a vowel (be-ing), plus a list of words that break the rules. It gets everyday words right and still misses some: champion comes out at two syllables. Every readability checker makes choices like these, which is why two tools rarely agree to the decimal point.

Sentence Length Checker: Finding Long Sentences

Average sentence length is the other half of both formulas, and the easier half to fix. The checker reports the average and lists every sentence over 25 words. That threshold is a working line. A long sentence that builds to a point can be the best sentence on the page. Trouble starts when long sentences come one after another, or when a reader has to hold the subject in mind for twenty words before the verb arrives.

Here is the long sentence from the example text, 52 words on its own:

Her brother had never been good with words, and the note was written in the same cramped hand he had used since school, with every line pressed so hard into the paper that she could feel the shape of the letters on the back of the page when she turned it over.

Split into three sentences, with the passive “was written” turned active:

Her brother had never been good with words. He had written the note in the same cramped hand he had used since school. He pressed every line so hard into the paper that she could feel the letters on the back of the page.

With that one change, the whole example goes from 85.1 to 88.4 Reading Ease and from grade 5.0 to grade 3.6, and the average sentence drops from 14.7 to 10.6 words. Paste both versions into the checker to see it. Variety matters as much as the average: a page where every sentence runs to the same length reads flat, however short they are. The guide to how many sentences belong in a paragraph covers the same question one level up.

Passive Voice Checker: Why It Says “Candidates”

The checker marks a form of be (am, is, are, was, were, be, been, being) followed by a past participle, allowing a word or two in between: was found, had been sold, was quickly forgotten. It knows the regular -ed participles and the common irregular ones such as written, taken, left and told.

It calls them candidates because the pattern also catches sentences that are not passive at all. She was tired and He was interested use a participle as an adjective, and the checker cannot tell them apart from The letter was found. It also misses passives built with get, as in he got fired. Read each mark and decide.

Passive voice is not an error. It is the right choice when the actor is unknown or beside the point: The car had been sold puts the weight on the car. It turns into a problem when it hides who did what, or when a page piles up so many that nothing seems to happen. The guide to active vs. passive voice has examples of both.

Adverb Checker: -ly Words

The adverb list shows every word ending in -ly, how often each one appears, and the share of your words they make up. It skips common words that only look like adverbs, such as friendly, lonely, early and family, and names like Emily in the middle of a sentence.

An adverb is worth a second look when it props up a weak verb. Walked slowly can become shuffled or trudged; said angrily often means the dialogue itself should carry the anger. The list of strong verbs is a good place to find the replacement. Adverbs stacked on adjectives are a mark of purple prose, and the checker makes those clusters easy to spot. Plenty of adverbs earn their place, so treat the count as a prompt to reread.

What a Readability Score Can't Tell You

Readability formulas measure two surface features: how long the words are in syllables and how long the sentences are in words. Nothing else goes in. Reverse the order of the words in a sentence and the formula gives exactly the same score. A short, rare word such as eft counts as easy, while a long, familiar one such as everybody counts as hard. The score cannot see whether the ideas come in a sensible order, whether the dialogue sounds like people, or whether a scene works.

That makes the score useful in two ways. The first is comparing drafts of the same text, where everything but the edits stays equal. The second is a benchmark: paste a page from a book your readers already love, note its score, and check your own pages against it. A middle-grade adventure, a literary novel and a business book will settle in different bands, and each can be right for its readers.

After the Readability Checker

Once sentence length and word choice look right, a full editing tool goes further. ProWritingAid and similar editors run grammar, style and repetition checks across a whole manuscript, well beyond what a readability formula looks at. After that, a human editor catches what software misses; the guide to copy editing vs. proofreading explains which kind you need. When the draft is final, the words to pages calculator tells you how long the printed book will be.

Readability Checker FAQ

What is a good readability score?

There is no single target for books. For nonfiction written for a general audience, the plain-English band of 60 to 70 Reading Ease is a sensible floor. For fiction, compare your pages with books in your genre that your readers already enjoy.

Is my text uploaded or stored?

No. The checker is a script that runs in your browser tab. The text is not sent to any server, not saved, and is gone when you close the tab.

Why do readability checkers give different scores?

They use the same formulas and count differently. Syllables are estimated by rules, and each tool's rules differ. Sentence breaks differ too: abbreviations such as “Dr.”, headings without a full stop, and dialogue punctuation can all be split or joined in different ways.

Is passive voice always wrong?

No. It is the natural choice when the actor is unknown or unimportant. The checker shows candidates so you can decide each one, and some of them, like “she was tired”, are not passive at all.

How much text should I check?

At least 100 words; below that the checker warns you that the score is unstable. A full chapter gives the most reliable picture, and the checker handles 10,000 words and more without slowing down.

Does it work for other languages?

No. Both formulas were built for English, and the syllable rules follow English spelling. Text in another language will get a score, but it will not mean much.