Readability checker

Readability formulas don't read for meaning — they estimate how hard text is to process using two proxies that are cheap to compute and correlate well with real difficulty: how long your sentences are, and how long (in syllables or letters) your words are. Every score below uses some combination of those two signals, which is why simplifying a piece of writing almost always means the same thing in practice: shorter sentences and shorter, more common words.

• Flesch Reading Ease. A 0–100 scale where higher is easier to read. It weighs average sentence length and average syllables per word. A score in the 60–70 range is considered plain English, easily understood by 13–15 year olds — a common target for web copy, help docs, and marketing pages.
• Flesch-Kincaid Grade Level. The same two inputs as Reading Ease, but rescaled to a U.S. school grade level. A score of 8 means the text should be understandable to an average 8th grader. This is the number most people mean when they use a flesch kincaid calculator — it's the most widely cited readability metric in journalism, government writing guidelines, and content style guides.
• Gunning Fog Index. Estimates the years of formal education a reader needs to understand the text on a first read. It leans on "complex words" — those with three or more syllables — alongside sentence length, so text with a lot of technical or Latinate vocabulary scores higher even if sentences are short.
• SMOG Index (Simple Measure of Gobbledygook). Also grade-level based, but calculated purely from the count of polysyllabic (3+ syllable) words across a sample of sentences. It was designed for health and safety communication, where getting the estimate right matters more than the formula being simple, and it tends to produce slightly higher (more conservative) grade estimates than Flesch-Kincaid.
• Automated Readability Index (ARI). Unlike the others, ARI estimates syllables indirectly by counting characters per word instead — useful because it doesn't depend on a syllable-counting heuristic at all. Like Flesch-Kincaid and Gunning Fog, it outputs an approximate U.S. grade level.

None of these formulas understand grammar, tone, or whether your argument makes sense — they're statistical approximations. Used together, though, they triangulate on the same underlying question: how much effort does this text ask of the reader? When all five scores roughly agree, you can trust the number. When they diverge sharply, it usually means your text mixes very short sentences with a handful of long, technical words — worth a manual read-through to see whether that vocabulary is necessary.

For most web content — landing pages, blog posts, product docs, marketing emails — the sweet spot is a Flesch-Kincaid grade level of 6 to 8, paired with a Flesch Reading Ease score of roughly 60 or higher. That's not because your readers can't handle harder text; it's because people skim on screens, read on mobile in bad lighting, and bounce off anything that takes visible effort to parse. Plain-English writing converts better, gets shared more, and is easier to translate or localize later.

Some content genuinely needs a higher grade level — legal terms, academic writing, technical documentation for expert audiences — and forcing those into a grade-8 reading level can strip out necessary precision. Use the target as a default for anything meant for a general audience, and treat exceptions as deliberate calls rather than accidents.

It also helps to know where familiar writing sits on this scale for calibration. Popular news sites typically land around grade 8–10. Bestselling fiction is often grade 5–7. Academic papers and legal contracts frequently score grade 12+ — sometimes intentionally, sometimes because nobody has ever run them through a reading level checker. If your onboarding email or pricing page scores closer to a legal contract than a news article, that is usually a sign to simplify.

• Split sentences over ~20 words into two shorter ones.
• Swap multi-syllable words for common synonyms ("use" instead of "utilize").
• Cut filler phrases ("in order to," "due to the fact that") down to one word.
• Prefer active voice — it's almost always shorter and clearer than passive voice.
• Read a paragraph out loud; if you run out of breath, the sentence is too long.
• Break up long paragraphs with subheadings, bullet points, and white space so the page feels lighter even before anyone reads a word.
• Replace strings of nouns stacked together ("customer onboarding workflow automation system") with a plain verb phrase.
• Re-run this reading level checker after each edit pass to confirm the grade level actually dropped.

A useful habit: draft first without worrying about the score, then run the draft through the checker and look specifically at which sentences are dragging the average up. You rarely need to touch every sentence — usually two or three overly long ones account for most of the grade-level gap.

It also helps to edit in passes rather than trying to fix everything at once. On the first pass, hunt for any sentence that runs more than two lines and split it. On the second pass, scan for jargon, buzzwords, and unnecessarily formal phrasing — "leverage," "facilitate," and "utilize" almost always have a shorter, plainer replacement. On the third pass, read the whole piece out loud one more time and trust your ear over the score: if a sentence sounds natural when spoken but scores slightly high, it is usually fine to leave as is.

• Content marketers & bloggers check drafts before publishing so posts stay skimmable and rank well, since search engines increasingly favor content that matches the reading level of the audience searching for it.
• UX writers & product teams keep onboarding flows, error messages, and empty states at a grade level users can parse in a glance, cutting support tickets caused by confusing copy.
• Technical writers use Gunning Fog and SMOG to check that documentation aimed at a general audience isn't accidentally written for engineers only.
• Students & academics use Flesch-Kincaid and ARI to sanity-check essays against assignment requirements or to simplify dense passages before submission.
• Health, legal, and government communicators lean on SMOG specifically, since it was designed for exactly this kind of public-facing, high-stakes writing where misunderstanding has real consequences.
• Email marketers check subject lines and body copy — simpler emails tend to have better open and click-through rates because they're easier to scan on a phone.
• Translators & localization teams simplify source text before translation, since plain-English source copy translates faster, cheaper, and with fewer ambiguous phrases.

Yes. Every score is calculated locally in your browser using JavaScript — your text is never uploaded to a server, logged, or stored anywhere. That makes it safe to paste in unpublished drafts, internal documentation, client work, or anything else you wouldn't want leaving your machine. You can also upload a .txt or .md file directly instead of pasting, and the file is read locally with your browser's FileReader API — it never touches a network request either.

Once you're happy with a result, use the Download report button to save a plain-text file containing every score alongside the original text, so you have a record of exactly what was checked and when.

Under the hood, the tool splits your text into words and sentences using simple punctuation rules, then estimates syllables per word with a vowel-group heuristic — counting runs of vowels, trimming a silent trailing "e," and treating every word as having at least one syllable. That syllable count feeds directly into Flesch Reading Ease, Flesch-Kincaid Grade Level, and SMOG, while Gunning Fog additionally flags "complex" words (three or more syllables, excluding common inflected endings like "-ing" or "-ed" when the base word is already simple). ARI skips syllables entirely and instead measures average characters per word alongside average words per sentence.

This mirrors the same approach used by classic readability tools going back decades: none of them parse grammar or understand meaning, they just count. That is a deliberate simplification, not a shortcut — the original research behind Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, and ARI all validated these same sentence-length and syllable-count proxies against real reader comprehension data, which is why the scores remain useful today even though the underlying math is simple enough to run instantly in a browser tab.

Because everything runs client-side in JavaScript, results update the moment you stop typing, paste a new block of text, or load a file — there is no server round-trip, no rate limit, and no minimum or maximum text length. Very short snippets (a headline, a single sentence) will produce noisier scores simply because the formulas need a reasonable sample of sentences to average over, so for the most reliable grade-level estimate, check at least a full paragraph at a time rather than a single line.

Microsoft Word and Google Docs both offer basic readability stats, but they are usually buried a few menus deep, only show Flesch Reading Ease and Flesch-Kincaid Grade Level, and require you to run a full spelling and grammar check just to see the numbers. This tool shows five scores side by side — Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, and ARI — updated live as you type, with no document to create, no account to sign into, and no menu to dig through.

It is also faster to use for one-off checks: paste an email draft, a product description, or a paragraph you're unsure about, glance at the grade level, and move on. For longer documents already living in Word or Google Docs, you can select the text, copy it in, or export the file as .txt and use the Upload .txt button to load it directly — either way the scoring happens instantly and privately in this browser tab.

• Chasing a single score. Optimizing purely for Flesch Reading Ease can produce choppy, robotic writing. Use the score as a guardrail, not the goal — good writing still needs rhythm and variety in sentence length.
• Ignoring your actual audience. A grade-6 target is right for a general consumer landing page; it's the wrong target for a developer API reference where precise technical terms are unavoidable and expected.
• Simplifying vocabulary but not structure. Swapping in shorter words while keeping 30-word sentences barely moves the needle — sentence length usually matters more than word choice.
• Checking once at the end. Readability is easiest to fix during editing, not as a final pass. Check a rough draft early so you know where the dense patches are before you polish the prose around them.