Microsoft Word's built-in readability pane reports only two formulas, Flesch Reading Ease and Flesch-Kincaid Grade Level, and it appears only after Word finishes a full spelling and grammar check on the document. To reach it in current versions of Word for Microsoft 365, Word 2021, Word 2019 and Word 2016, you open File > Options > Proofing, confirm that "Show readability statistics" is ticked under "When correcting spelling and grammar in Word", then run a spelling and grammar pass. The dialog that appears lists counts for Words, Characters, Paragraphs and Sentences, plus the two scores. There is no syllable count, no complex-word count and no letter count.
That is the entire native surface for "check readability score in Word". It is enough for a quick sanity check, but it is not enough to act on when the audience matters. A technical writer, a teacher grading student work, a content marketer targeting a 7th-grade reading level, or a healthcare communicator who has to hit plain-language targets all need more than two numbers from one formula family, and Word does not give them more.
Why One Formula Is Not Enough
The six formulas readability researchers treat as standard are Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. They disagree with one another by design. Flesch-Kincaid and SMOG weigh syllables per word; Gunning Fog weighs the share of long words per sentence; Coleman-Liau and the Automated Readability Index use character counts instead of syllables, which makes them a useful cross-check whenever a syllable estimate looks suspect. Reading the six together is far more informative than trusting any single one.
A short comparison makes the difference visible.
| Formula | Returns | Primary signal |
|---|---|---|
| Flesch Reading Ease | 0–100 ease score (higher is easier) | Syllables per word |
| Flesch-Kincaid Grade Level | US school grade level | Syllables per word |
| Gunning Fog | US school grade level | Long words per sentence |
| SMOG | US school grade level | Three-syllable words in a 30-sentence sample |
| Coleman-Liau | US school grade level | Characters per word |
| Automated Readability Index (ARI) | US school grade level | Characters per word |
Each formula returns a different kind of value, so the columns are not interchangeable. Flesch Reading Ease is a 0 to 100 style score where higher means easier reading, with an interpretation band so the number has plain meaning. The other five return a United States school grade level, which means a Flesch-Kincaid score of 8.2 and a Gunning Fog score of 9.1 are reporting the same kind of value (grade level) on different signals. When two grade-level formulas disagree by more than a grade, the disagreement almost always traces back to syllable counting, not to the formula itself.
How to Check Readability Score in Word and Across Six Formulas
For a single, thorough readability pass, paste the passage you are working on into a browser-based tool that returns all six formulas plus the raw counts they were built from. The Readability Score Checker does exactly this and runs the calculation locally so the text never leaves your browser, which matters for unpublished drafts and client material.
The procedure has three steps.
- 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.
Start with the Flesch Reading Ease band because it is the only score that comes with a plain-language interpretation, so a label such as "Standard" or "Fairly Difficult" tells you the answer before you read a single grade number. Then look at the five grade-level scores side by side. If they cluster within a grade or two, that is your reading level. If they spread wider than that, look at the counts underneath — words, sentences, syllables, letters, characters, three-syllable complex words and polysyllables — and find which count is out of line with the others.
The interpretation bands the tool uses for Flesch Reading Ease follow the plain-language convention published by the US-funded MSKTC (Model Systems Knowledge Translation Center) at MSKTC's plain-language tool, not Flesch's own wording. They are applied as open-ended thresholds because the score is genuinely unbounded: it can exceed 100 and it can go below zero.
| Flesch Reading Ease score | Interpretation | Approximate grade level |
|---|---|---|
| 90 and above | Very Easy | 5th grade |
| 80 to 89 | Easy | 6th grade |
| 70 to 79 | Fairly Easy | 7th grade |
| 60 to 69 | Standard | 8th–9th grade |
| 50 to 59 | Fairly Difficult | 10th–12th grade |
| 30 to 49 | Difficult | College |
| Below 30 | Very Difficult | College graduate |
The Counts That Drive Every Score
Seeing the counts matters because readability scores are simple functions of those counts, and two tools that disagree almost always disagree about counting rather than about the formula. The counts surfaced by a thorough check are words, sentences, syllables, letters, characters, three-syllable complex words and polysyllables. Every formula uses a different combination of them, which is why hiding the counts hides the only place a reader can verify the answer.
A worked example on one short sentence makes the chain visible. Take "The quick brown fox jumps over the lazy dog." The counts are nine words, one sentence, eleven syllables (one for The, quick, brown, fox, jumps, the and dog; two for over and lazy), thirty-five letters and forty-four characters including spaces.
For Flesch Reading Ease, the verified formula (Kincaid et al., 1975, "Derivation of New Readability Formulas", Navy technical report DTIC AD-A006655) is:
206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
Substituting:
206.835 − 1.015 × (9 ÷ 1) − 84.6 × (11 ÷ 9) = 206.835 − 9.135 − 84.6 × 1.2222 = 206.835 − 9.135 − 103.4 = 94.3
A score of 94.3 lands in the "Very Easy" band, which matches the way the sentence reads. Notice the coefficient used here: 84.6, not the 83.6 an OCR scan appears to show in some reproductions. The same primary-source check applies to the Coleman-Liau coefficient of 0.0588, not the 0.0855 that circulates in at least one journal table. Where published tables contradicted each other, the disagreement was resolved with two independent sources rather than a majority vote of search results.
When the Numbers Should Be Treated as Indicative Only
Grade-level formulas were validated on running prose, so results on lists, code blocks, tables or heavily numeric text should be read as indicative only. The Automated Readability Index and Coleman-Liau can legitimately return a negative grade on very short, very simple sentences, which is the published arithmetic rather than a tool error. SMOG carries an extra caveat: McLaughlin defined it for a sample of exactly thirty sentences, so below thirty sentences the score is an extrapolation, and because the formula takes a square root of the complex-word count, the scaling amplifies any counting noise.
English has no authoritative algorithm for counting syllables from spelling, so the syllable count in any tool is a rule-based estimate. A thorough implementation splits hyphenated words, handles "consonant + le" endings, decides whether a final "es" or "ed" adds a syllable, drops silent final "e" and counts the remaining vowel groups, with a floor of one syllable per word. That approach is right on ordinary prose but under-counts some vowel-adjacent words, which is one reason the syllable count is shown rather than hidden.
Sentence detection is likewise heuristic: decimals, initials and a short abbreviation list are shielded so that a price or a title does not end a sentence early. Readability and reading time use overlapping word and sentence counts, which is why writers who plan content for a specific audience often run a reading-time estimate from word count alongside a readability pass — the two together tell you both how long the passage takes and how dense it is.
The strongest argument for cross-checking the six formulas is that any one of them can be skewed by a single outlier sentence. Use the scores as a direction rather than 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.