Readability Checker — Free Flesch, Fog, SMOG & Grade-Level Scores

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Not all texts are equally easy to read — and “readable” is not a matter of opinion. For over 70 years, researchers have used mathematical formulas to estimate how hard a passage is to read, based on measurable features like sentence length and word difficulty. This free readability checker runs your text through every major formula at once — Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau, the Automated Readability Index, Dale-Chall and Fry — so you get the full picture instead of a single number from a single method.

Paste your text into the tool above and you will get all eight scores instantly, in your browser.

Worked example: one paragraph, eight scores

Here is a 74-word paragraph of the kind a manager might send to staff, run through the checker:

The manager asked her team to draft a detailed summary of the quarterly business results before the Friday meeting. She wanted the document written in clear, direct language so that every member of staff could understand it at once. Longer sentences were broken into shorter units, and every unclear phrase was rewritten with a simpler wording. The final draft scored a grade level of twelve on the checker, which suited the intended readers well.

Formula Score What it means
Flesch Reading Ease 55 “Fairly difficult” band (0 = hardest, 100 = easiest)
Flesch-Kincaid Grade 11 ≈ 11th-grade reading level
Gunning Fog 12 ≈ 12 years of education needed
SMOG 11 ≈ 11 years of education needed
Coleman-Liau 11 ≈ 11th-grade reading level
Automated Readability Index 12 ≈ 17–18-year-old reader
Dale-Chall 9 ≈ 9th–10th grade (uses a familiar-word list)
Fry graph 11 ≈ 11th grade (plots sentences vs syllables)

So why does Fog say 12 while Flesch Reading Ease says 55? They measure the same text in different units. Fog converts sentence length and the share of complex words into an approximate school grade level — 12 means a text suited to a final-year high-school reader. Flesch Reading Ease converts sentence length and syllable density into a 0–100 ease scale — 55 sits in the “fairly difficult” band. Both describe this paragraph as moderately demanding; Fog just speaks in grades and Flesch in ease points. The grade-level formulas cluster around 11–12 here, which is the real signal: a typical professional-office paragraph, neither simple nor academic.

Which formula should I use?

  • Flesch Reading Ease + Flesch-Kincaid: the default pair for general writing, essays and blog posts. Our Flesch-Kincaid calculator explains the grade-level version in depth.
  • Gunning Fog: popular for business, journalism and plain-language audits — it penalises long sentences and complex words directly. Try our Gunning Fog calculator for a formula walk-through.
  • SMOG: the standard for healthcare and medical patient materials in several countries — it is stricter about polysyllabic words. See the SMOG calculator.
  • Coleman-Liau: counts characters instead of syllables, which makes it fast and consistent — handy for very long documents. See the Coleman-Liau calculator.
  • Automated Readability Index (ARI): also character-based, calibrated against US grade levels. See the ARI calculator.
  • Dale-Chall: compares your words against a list of ~3,000 familiar words — the only formula that cares whether a word is known, not just long. See the Dale-Chall calculator.
  • Fry: the classic graph method from classrooms — plot sentences against syllables. See the Fry readability calculator.

Who uses a readability checker

  • Students checking that an essay sits at the expected grade level before submitting.
  • Bloggers and marketers targeting Flesch Reading Ease 60+ so posts stay accessible to a wide audience.
  • Healthcare writers, where patient materials in several countries are required to meet a SMOG target.
  • Government and finance teams running plain-language compliance audits on public documents.

Honest limitations

  • These formulas count syllables and sentence length only. They cannot tell whether your writing is actually clear, correct, well-organised or truthful. A short, badly written paragraph can score “easy” and still confuse readers.
  • Texts under roughly 100 words give unstable scores — one long sentence can swing the result several grades. The formulas were designed for passages of at least 100 words (SMOG originally needed 30 sentences).
  • Different checkers can report slightly different scores for the same text, because syllable counters disagree on words like “business” or “every” and formulas handle hyphenation and numbers differently.
  • Technical or specialist vocabulary is penalised even when your audience knows it — a cardiology leaflet will always score harder than its real readers experience.

Frequently asked questions

What is a good readability score?

On Flesch Reading Ease (0–100), 60–70 is considered plain English for most adults; on the grade-level scales, grade 8–9 is the usual target for general-audience writing.

Which formula should I use?

For general writing, start with Flesch-Kincaid Grade Level. Use SMOG for healthcare or patient-facing material, Gunning Fog for business and plain-language audits, and Dale-Chall if vocabulary familiarity matters more than sentence length.

Why do two checkers disagree on the same text?

Three reasons: they may use different formulas; their syllable counters may disagree on ambiguous words; and they may count sentences, abbreviations and numbers differently. Disagreements of 1–2 grades between tools are normal.

What grade level should a blog post target?

Grade 8–9 (roughly Flesch Reading Ease 60–70) is the standard recommendation for general-audience content — readable by most adults without feeling dumbed down.


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