Readability Checker
Flesch, grade level, Fog and SMOG scores with highlights. Runs in your browser.
About this readability checker
This readability checker scores your writing with six standard formulas: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. It is for anyone writing for a wide audience, such as bloggers, marketers, teachers, support teams and people writing public health or legal notices.
Paste your text and the scores update as you type. Long sentences are shaded and passive voice is underlined right in your text, so you can see what to fix, not just a number. A worked breakdown shows the counts and the arithmetic behind each score, so you can check the numbers yourself.
Want the raw counts as well, such as characters, paragraphs and speaking time? The word counter has them.
Features
Six formulas side by side
Each score comes with its formula, the year and the researcher who published it, and what the number means as a US school grade and reader age. An average of the five grade-level scores gives one number to aim at.
Long sentences highlighted
Sentences over your limit (20 words by default) are shaded yellow, and those 10 words beyond it are shaded red. Move the slider to suit your audience.
Passive voice spotted
Phrases like was written, is being reviewed and are not often used are underlined. The check looks for a form of be followed by a past participle, including about 160 irregular ones such as kept, built and chosen.
Complex words listed
Words of three or more syllables can be shown in bold, and the most repeated ones are listed below the text. That list is usually the fastest route to a better score: swap utilise for use and approximately for about.
How to use the readability checker
- 1Paste your text. Scores update as you type.
- 2Read the Flesch score, the average grade level and each formula's result.
- 3Fix the highlighted long sentences and passive phrases, and watch the scores move.
When to use it
Blog posts and landing pages
Most web readers skim. A Flesch score of 60 or more and an average grade around 8 make a page easier to scan on a phone. Pair this with a keyword density check before you publish.
Patient leaflets and public notices
Health literacy guidance commonly recommends writing patient material at a 6th to 8th grade level. SMOG was designed with this kind of material in mind and is widely used to check it.
How is the Flesch Reading Ease score calculated?
Rudolf Flesch published the formula in 1948 in the Journal of Applied Psychology. It uses just two measures: average sentence length in words, and average word length in syllables. The score is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words).
Higher means easier. A passage averaging 15 words per sentence and 1.5 syllables per word scores 206.835 − 15.2 − 126.9, which is about 64.7, plain English. Push that to 25 words per sentence and 1.7 syllables per word and the score falls to about 38, which is college level.
- 90 to 100: very easy, 5th grade
- 80 to 90: easy, 6th grade
- 70 to 80: fairly easy, 7th grade
- 60 to 70: plain English, 8th to 9th grade
- 50 to 60: fairly difficult, 10th to 12th grade
- 30 to 50: difficult, college
- 0 to 30: very difficult, college graduate
What do the grade-level formulas measure?
Flesch-Kincaid Grade Level (Kincaid, Fishburne, Rogers and Chissom, 1975) was derived for the US Navy and turns the same two measures into a school grade: 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. A score of 8 means an average 8th grader, roughly a 13 to 14 year old, should follow it.
Gunning Fog (Robert Gunning, The Technique of Clear Writing, 1952) counts complex words of three or more syllables, leaving out proper nouns, hyphenated compounds and words that only reach three syllables with -es, -ed or -ing. SMOG (G. Harry McLaughlin, Journal of Reading, 1969) counts every word of three or more syllables and was built on 30-sentence samples. Coleman-Liau (1975) and the Automated Readability Index (Smith and Senter, 1967) count letters or characters instead of syllables, which made them easy for early computers and typewriter counters.
- Gunning Fog: 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
- SMOG: 1.0430 × √(polysyllables × 30 ÷ sentences) + 3.1291
- Coleman-Liau: 0.0588 × L − 0.296 × S − 15.8, with L letters and S sentences per 100 words
- ARI: 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43
Why do readability checkers give different scores?
The formulas are fixed, but the counting is not. Is e.g. the end of a sentence? Is a heading a sentence? Does fire have one syllable or two? Each checker answers differently, and a change of just 0.1 in average syllables per word moves Flesch-Kincaid by 1.2 grades, so small counting choices add up.
This checker splits sentences at . ! ? and at line breaks after headings, list items and blank lines, and it knows common abbreviations such as Dr., e.g. and U.S. Syllables come from English spelling rules plus an exception list. Expect it to land within about a grade of other good checkers. Use the scores to compare drafts of your own text rather than as an exact measurement.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Formulas | Six, with formulas and sources shown | One to three, no sources |
| Highlights | Long sentences, passive voice, complex words | Score only |
| Shows the arithmetic | Yes, with your counts | No |
| Word limit | None | Often 1,000 to 2,500 words on free plans |
| Sign-up | None | Account needed for full reports |
| Privacy | Runs in your browser | Text sent to a server |
Tips
- Split the red-shaded sentences first. One 45-word sentence can lift the grade level of a short page by a whole point.
- Swap long words for short ones where the meaning stays: use for utilise, help for facilitate, buy for purchase.
- Keep the old version when you edit, then paste both into text diff to see exactly which sentences you changed.
- Rewrite passive phrases when the actor matters. The form was rejected by the bank becomes The bank rejected the form, which is shorter and clearer.
Questions
What is a good readability score?
For a general audience aim for a Flesch Reading Ease of 60 or more and a grade level of 8 or lower. Children's material should sit around grade 5. Academic and technical writing often scores 30 to 50, which is fine for specialists.
What is the difference between Flesch Reading Ease and Flesch-Kincaid?
Both use sentence length and syllables per word. Reading Ease gives a 0 to 100 score where higher is easier. Flesch-Kincaid Grade Level turns the same inputs into a US school grade where lower is easier.
What grade level should I write at?
Grade 7 to 8 suits most adult readers, and grade 6 to 8 is the common advice for health information. Writing at a lower grade does not talk down to experts; it just saves them time.
How is the Gunning Fog index calculated?
Add the average sentence length to the percentage of complex words, then multiply by 0.4. Complex words have three or more syllables, not counting proper nouns, hyphenated words or the -es, -ed and -ing endings.
Why does SMOG need 30 sentences?
McLaughlin built the formula from samples of 30 sentences, so it is most reliable at that length. With shorter text the score is scaled up to 30 sentences, which works but is rougher. The tool notes this when your text is short.
Does readability affect SEO?
Google has not said it uses readability formulas for ranking. Clear writing still helps indirectly, because people stay and read text they understand. Write for the reader first and use the score as a check.