Score your text against seven readability formulas - Flesch, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, ARI, and Dale-Chall. Runs in your browser.
| Formula | Score | Interpretation |
|---|---|---|
| Flesch Reading Ease | -- | 0-100, higher = easier |
| Flesch-Kincaid Grade | -- | US school grade |
| Gunning Fog Index | -- | Years of education needed |
| SMOG Index | -- | Grade for full comprehension |
| Coleman-Liau Index | -- | US grade (character-based) |
| Automated Readability Index | -- | US grade (character-based) |
| Dale-Chall Score | -- | Adjusted against 3,000 familiar words |
| Score | Grade | Level | Example |
|---|---|---|---|
| 90 - 100 | 5th grade | Very Easy | Children's books, Harry Potter |
| 80 - 89 | 6th grade | Easy | Consumer magazines, Reader's Digest |
| 70 - 79 | 7th grade | Fairly Easy | Sports news, casual blog posts |
| 60 - 69 | 8th - 9th grade | Standard | USA Today, BBC News, Reuters |
| 50 - 59 | 10th - 12th grade | Fairly Difficult | Business writing, Time magazine |
| 30 - 49 | College | Difficult | The Economist, academic essays |
| 0 - 29 | College graduate | Very Difficult | Legal contracts, medical journals |
| Use case | Best formula | Why |
|---|---|---|
| Marketing & web copy | Flesch Reading Ease | Familiar 0-100 scale, used by Yoast and most CMS plugins |
| K-12 educational material | Flesch-Kincaid Grade | Outputs a US school grade directly |
| Business / journalism | Gunning Fog | Penalizes complex words, designed for newspapers |
| Healthcare / patient docs | SMOG | Built for high-stakes comprehension; conservative |
| Technical & acronym-heavy | Coleman-Liau or ARI | Use character counts instead of syllables, robust to jargon |
| General-audience writing | Dale-Chall | Doesn't penalize long-but-common words ("incredible", "everything") |
No formula is "correct" - run several and look for agreement. If Flesch-Kincaid, Gunning Fog, and SMOG all give the same grade level, your estimate is reliable. Disagreement usually means your text has unusual structure (short sentences with rare words, or long sentences with simple words).
The Flesch Reading Ease formula rates text on a 0-100 scale. Higher scores mean easier text. It uses average sentence length and average syllables per word. Aim for 60-70 for general web content.
Both formulas use the same inputs but output different units. Flesch Reading Ease gives a 0-100 score where higher is easier. Flesch-Kincaid Grade Level outputs a US grade level - so 8.0 means an eighth-grader can read it. Use Flesch Reading Ease for marketing copy and grade level for educational material.
The Gunning Fog Index estimates the years of formal education a reader needs to understand a text on first reading. It is based on average sentence length and the percentage of complex words (three or more syllables). A score of 8 is ideal for a wide audience; above 17 means very difficult.
SMOG (Simple Measure of Gobbledygook) was designed for healthcare materials and predicts the school grade level needed for full comprehension. It counts polysyllabic words across 30 sentences. SMOG tends to score slightly higher than Flesch-Kincaid for the same text.
Unlike most formulas, Coleman-Liau uses character counts instead of syllables, which makes it easier to compute mechanically. It outputs a US grade level. Useful when syllable estimation is unreliable, e.g. technical text full of acronyms.
ARI also uses character counts (per word and per sentence) rather than syllables, so it can be calculated by typewriters and early computers. It outputs a US grade level. Originally developed for the US Air Force.
Dale-Chall measures difficulty against a list of 3,000 words familiar to fourth-graders. Words outside the list are treated as difficult. Effective for general-audience writing because it does not penalize long-but-common words. Scores under 4.9 are easy; over 9.9 require college-graduate reading skill.
For general web content aim for a 7th-8th grade level (Flesch 60-70 or Gunning Fog 8). Marketing copy goes lower; academic writing naturally scores higher. Reuters and the New York Times target 8th-9th grade; instruction manuals target 6th.
Shorten sentences (under 20 words on average). Replace complex words with simple ones. Break long paragraphs. Prefer active voice. Cut filler. Almost every formula rewards shorter sentences and shorter words, so optimizing for one usually improves all of them.
No single formula is correct - they measure slightly different things. Run several and look for agreement. If Flesch-Kincaid, Gunning Fog, and SMOG all return roughly the same grade level, you can be confident. If they diverge, your text probably has unusual structure (very short sentences with rare words, or very long sentences with simple words).