A readability score is a single number that estimates how hard an English passage is to read, calculated from simple counts of words, sentences and syllables inside the text. To check a readability score online free, paste your English text into a tool that runs several published formulas at once — Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index — and read the band and grade-level scores together rather than trusting any one of them. The Readability Score Checker does exactly this: paste your text, run Analyze, and the page returns six scores side by side, together with the raw counts of words, sentences, syllables, letters, characters, complex words and polysyllables that every formula is built from. Seeing the counts matters, because readability formulas are short arithmetic expressions of those counts, and two tools that disagree almost always disagree about counting rather than about the formula itself. Everything is computed in the browser, so the text is never uploaded, stored, or attached to an account, which matters when the passage is an unpublished draft or client material.
How to check readability score online free
The fastest path to six published readability scores is a browser tool that runs every formula at the same time and shows the arithmetic that produced each result.
- Paste the English passage you want to score into the text box.
- Select Analyze to compute all six formulas at once.
- Read the Flesch Reading Ease band first, then compare the grade-level scores and check the raw counts underneath.
The first step looks ordinary, but it is where most disagreements between tools begin. A passage copied from a word processor can carry smart quotes, em dashes and non-breaking spaces that quietly change letter and character counts, and a paragraph broken with hard line breaks inside what reads as one sentence can shift the sentence count. Pasted plain text — the kind you get from a plain-text editor — gives the formulas the cleanest signal. The second step is the actual computation: the page evaluates Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and ARI from the same counts, so the six numbers you see are strictly comparable because they were built from identical inputs. The third step is the part most people skip. Flesch Reading Ease is a 0-to-100-style score where higher is easier, with an interpretation band attached so the number carries meaning. Reading it first gives you a quick, plain-language verdict; the five grade-level numbers then refine that verdict in different ways.
What the six formulas actually measure
Every readability formula is a short arithmetic expression of the same handful of counts. What changes between formulas is which counts they use and how they combine them. Knowing this turns a wall of numbers into a structured comparison rather than a single ambiguous grade.
| Formula | Main inputs | Returns | Direction |
|---|---|---|---|
| Flesch Reading Ease | Words per sentence + syllables per word | 0–100 score, unbounded | Higher is easier |
| Flesch-Kincaid Grade Level | Words per sentence + syllables per word | US school grade | Higher is harder |
| Gunning Fog | Words per sentence + complex words per word | US school grade | Higher is harder |
| SMOG | Polysyllables per sentence | US school grade | Higher is harder |
| Coleman-Liau | Letters per word + sentences per word | US school grade | Higher is harder |
| Automated Readability Index (ARI) | Characters per word + words per sentence | US school grade | Higher is harder |
Three patterns stand out. First, Flesch-Kincaid and Flesch Reading Ease share inputs but report in different units — one returns a grade, the other a 0-to-100 score — so they will track each other on long text but diverge on short text because the scaling constants are not symmetric. Second, Gunning Fog and SMOG weight long words rather than syllables, which makes them behave differently from the Flesch pair on technical prose where the same words can carry three or four syllables each. Third, Coleman-Liau and ARI ignore syllables entirely and count letters or characters instead, which makes them a useful cross-check whenever the syllable estimate looks suspect — for example, in text with heavy jargon, unusual coinages, or consistent hyphenation.
Reading the Flesch Reading Ease band
Flesch Reading Ease is the only one of the six scores that comes with an interpretation band attached, which is why reading it first is usually the fastest way to interpret a passage. The bands below follow the plain-language convention published by the US-funded MSKTC Plain Language tool, and they are applied as open-ended thresholds because the score itself is genuinely unbounded: it can exceed 100 on very short, simple text and go below zero on dense prose.
| Flesch Reading Ease score | Plain-language label | Approximate US grade |
|---|---|---|
| 90–100 | Very easy | 5th grade |
| 80–89 | Easy | 6th grade |
| 70–79 | Fairly easy | 7th grade |
| 60–69 | Standard / plain language | 8th–9th grade |
| 50–59 | Fairly difficult | 10th–12th grade |
| 30–49 | Difficult | College |
| 0–29 | Very difficult | College graduate |
To see how quickly the score moves, take the single sentence The cat sat on the mat. With six words, one sentence and six syllables, the averages are 6.00 words per sentence and 1.00 syllables per word. Substituting into the published Flesch formula:
206.835 − 1.015 × 6.00 − 84.6 × 1.00 = 206.835 − 6.090 − 84.600 = 116.145
A result of 116.145 is above 100, which is allowed by the published arithmetic and is the simplest demonstration that the score can exceed its nominal ceiling on very short text. The page reports the band as open-ended rather than capping the number at 100, so readers do not see a misleading "100.0" for genuinely easier-than-easy text.
Why the six scores disagree by design
Two readable texts can score differently on the same formula, and two identical copies of the same text scored by two tools can also produce different numbers. The first kind of disagreement is the formula's job: Flesch-Kincaid and SMOG weigh syllables, Gunning Fog weights long words per sentence, and Coleman-Liau and ARI count characters instead of syllables. Reading all six together is far more informative than trusting any single one, because a syllable-based formula and a character-based formula will only disagree meaningfully when the text contains unusual word shapes — heavy jargon, technical coinages, or consistent hyphenation — that change the syllable count in one direction and the character count in another.
The second kind of disagreement is almost always a counting disagreement. Readability formulas are deterministic functions of counts, so if two tools return different numbers on the same text, they almost certainly counted words, sentences or syllables differently. Smart quotes versus straight quotes, em dashes versus two hyphens, decimal points inside sentences, and abbreviations such as "Dr." or "U.S." all sit on top of the counting rules. This is why the Readability Score Checker shows the raw counts underneath the scores. You can confirm that two tools saw the same passage by comparing counts first and formulas second; the formulas are public and short, and the counting is the hard part.
What the raw counts reveal
Underneath the six scores, the page reports words, sentences, syllables, letters, characters, three-syllable complex words and polysyllables. Each count feeds a specific formula, and reading them together exposes where a high grade level actually came from. A paragraph that scored as college-level because of long sentences will show a high average sentence length and roughly average syllable counts. A paragraph that scored college-level because of jargon will show average sentence length and a high count of three-syllable words. The two call for different edits — sentence splitting versus word substitution — and only the counts tell you which one. Polysyllables specifically drive the SMOG score, while complex words feed Gunning Fog, so a paragraph whose two scores diverge sharply usually has words that the two counters classify differently.
The raw counts also matter for short text. On a single sentence of six words, all six formulas will read the same input but apply different weightings to a very small sample, so the spread between them will be wider than it would be on a full paragraph. This is expected arithmetic, not an error in the tool, and it is one reason the counts are shown next to the scores rather than buried below them.
Limits to keep in mind
Three limits are worth surfacing before you act on a score. The first is SMOG: McLaughlin defined it for a sample of exactly thirty sentences, so below that the score is an extrapolation and the page says so while still showing it. The formula also takes a square root, which amplifies counting noise on short samples. The second is that Coleman-Liau and ARI can legitimately return a negative US grade level on very short, very simple sentences. That is the published arithmetic, not a bug; the same constants that pull dense prose up to a high grade pull trivial prose below zero. The third is the syllable count itself: English has no authoritative algorithm for counting syllables from spelling, so the counter is a rule-based estimate that handles hyphenation, consonant-plus-le endings, silent final e and common es / ed endings, with a floor of one syllable per word. It is reliable on ordinary prose and under-counts some words with adjacent vowels. Sentence detection is similarly heuristic, with decimals, initials and a short abbreviation list shielded so a price or a title does not end a sentence early.
Because grade-level formulas were validated on running prose, results on lists, code blocks, tables or heavily numeric text should be treated as indicative only. Use the scores as a direction, not a verdict — they are good at telling you that a paragraph got denser after an edit, and poor at telling you whether a specific reader will understand it. For readers who want a second opinion on text already inside Microsoft Word, see the dedicated Word readability guide, which covers the built-in checker and what it leaves out.
Finally, the published coefficients matter. The Flesch-Kincaid and ARI coefficients come from the 1975 Navy technical report that derived them, the SMOG constants come from McLaughlin's original 1969 paper, and the Flesch Reading Ease coefficients and its interpretation bands come from a US government plain-language document. Where published tables contradict each other, the Readability Score Checker resolves the disagreement with primary sources rather than with a majority vote of search results — for example, the Flesch coefficient is 84.6 and not the 83.6 an OCR scan appears to show, and the Coleman-Liau coefficient is 0.0588 and not the 0.0855 that circulates in at least one journal table. That work is what makes the counts and the scores auditable.