Last update: 17. December 2025 - currently updating

Calculating the readability online - online tools

This page lists online tools that you can use to analyze your texts. It is easy, you just copy and paste your text into a window, sometimes also a URL can be specified. The most tools are limited to texts in English. If a language is not mentioned in the description of a tool, only a readability analysis of English texts gives valid results. 

Please note the data privacy statements of some websites. Your data may be stored or even given away to third parties without your allowance. Thanks to Karen Smiley for this information.

Many programs were excluded from this page, these are at the bottom of this page. One reason is that the overviews I used are listing SEO tools, and readability is only one aspect. 

Testing readability online tools

Maybe you would like a test of all tools? I found none on the web, so I have started to develop a test. I also added some remarks so that you can get an impression on the software. Also some entries were removed, e.g. ClickHelp removed the readability formulas, and CIRTC redirects to readabilityformulas.com.

The readability formulas are often named by the authors. You should know that there are some readability formulas that have different versions: Dale-Chall, Spache, Automated readability index (ARI). Also Flesch's reading ease formula has been adapted for special purposes from different authors.

Often you will find that the version of the formula is not mentioned. Some sites collect your texts, but most give no information what happens with your data. 

Test features

The following features are tested if they are correct or if they exist:
  1. Which formulas are used in the analyses?
  2. Are the implications of each readabilty formula explained?
  3. Sources of text, e.g copy & paste, upload a file or specify a URL
  4. Are subanalyses (e.g. paragraph) possible?
  5. Is a selection by age or text genre possible?
  6. number of grammatical sentences
  7. number of words
  8. number of unknown words, hard words, depending on the readability formula
  9. number of syllables if readability formulas use them
  10. results of the appropriate readability formulas
  11. Interpretation of the results, e.g. is values are explained
  12. remarks: topics like restrictions, data storage and the like
Three different texts will be used for the analyses:
  1. The Gettysburg address - the dashes between words were separated from the words before and afther the dashes
  2. A story that contains different flexions of verbs to test if the number of unknown words (Dale/Chall, Spache) is correct.
  3. An article from CNN dated from October 2025

All texts were manually counted, so one can compare the correct results with the results from the websites and the desktop applications. The results differ, some only slightly, some a lot. If you run one of the sites and think the information is false or has errors, please contact me, email webmaster at this domain name.

Linguistic problems of readability formulas

Also some problems occured. Some websites just didn't work, I disabled my adblocker, and I also tried different browsers: Firefox, Edge, Vivaldi and Opera. 

Counting words also seems to be a problem. The Gettysburg address contains four dashes, and in American typography the dashes are not separated using blanks like in other languages. For the test I inserted blanks before and after the dashes, otherwise these constructions would be counted as very long words and vould bias the results of any readability analysis.

The criteria are manifold: the readability formulas that are offered, text statistics to be able to check the numeric results, solutions like sentence and syllable counting that are often tricky. Some readability formulas work with lists, but mostly these lists consist of base words, but one must add the regular forms of nouns, verbs, and adjectives. 
Another problem is to use the correct readability formula. Such a formula is developed for a specific language, a text genrece, and a target group. These implicatons must be considered, because usihg a readability formula for school books is not appropriate for technical manuals or patient leaflets. If one can specify these three criteria, and the software knows the appropriate readability formulas, this selection would be very helpful especially for non-experts.

Counting words, syllables, and sentences seem to be easy. Most readability formulas use these text properties, so it is important to know if they work correctly. English texts often contain dashes, but these are not separated from the words before and behind, so it looks like a compound word (a word with a dash between its components). In the test these dashes were separated from the words. 

Because English words often differ in speaking and writing, an algorithm for counting syllables consists of many exceptions and may result in incorrect counting. One has to have  in one's mind if you use syllables that are spoken, of if you use hyphenation rules for written texts. E.g. the word our seems to have one syllable only, because hyphenation is not possible, but if you speak it, the r can only be uttered if you move your lips. There are also many exceptions so working with lists for each language work best.

A sentence's end often is a full stop - or a point. But not every point means that you reach the end of a sentence. Abbrevations like Dr., Prof., rsp. or etc. often have a point also, so the software must be able to detect the real end of sentence. One can handle this problem with built-in lists so counting sentences is correct. This was also tested.

The results of readability formulas are different, depending on the readability formula:
  1. index value: the higher the value, the more understandable is the text. The range is often between 0 (extremly difficult) and 100 (very easy), e.g. Flesch's Reading Ease.
  2. grade: the school grade in the US education system
  3. age: in years, often derived from the school grade

If you want to make your text more readable, you want to know which parts of the text may need an update. Therefore words and/or sentences that are too long are highlighted. Two software programs provide a detailed readability analysis for each paragraph so you can see which of the paragraphs are easier or more difficult to read.

Other caveats of readability formulas that require a counting of syllables, need lists of words or have to be standardized because the original formula fits for one sample size only - mostly 100 words.

1. Syllable count: in English this is very difficult because writing and speaking sometimes differ a lot. Just counting vowels will not work with words with a silent e at the end like: love, ride, leave, were, where etc. In some readability formulas all syllables are needed, in other only words with three or more syllables, or with one syllable only. If you really want precise results, you must work with a look-up table. Other readability formulas determine the length of a word by counting the characters (letters) of a word. The following readability formulas use the count of syllables:
Flesch Rreading Ease and derivates (as mentioned above), Flesch-Kincaid, SMOG, Gunning FOG, Forcast, Linsear Write, Lix, Rix, Wheeler-Smith. 

2. Word lists: Dale-Chall and Spache published two different versions, most vendors don't specify the version they use. The differences are the word lists, both have them and count the words that are not mentioned in the word list. However, implementing these word lists is not just copying the words from the publication into a file that is used by the software. Both authors only published the basic forms of the words, e.g. the infinitive of verbs, the singular of nouns, and the absolute form of adjectives. All other forms must be added but it seems that only one vendor did that.

3. Standardization: Some readability formulas are in a form that require a sample size of a certain size, mostly 100 words. So many readability formulas need either an exact sample of text, or one has to standardize the formula mathematically. This is necessary if one variable in the equation is just a counter for the whole text, but the formula is for 100 words samples, e.g. Coleman-Liau, Forcast, Flesch's Reading Ease Index (and all derivates), SMOG.

Autocrit

website: Autocrit
organization: Accelerated Innovations Corporation - AutoCrit, Celebratin, FL, USA
  1. Which formulas are used in the analyses? new Dale-Chall, Spache revised, Flesch-Kincaid, Linsear Write, Flesch reading ease
  2. Are the implications of each readabilty formula explained? Yes
  3. Sources of text: file, copy & paste
  4. Are subanalyses (e.g. paragraph) possible? Yes, but testing failed (chapters)
  5. Is a selection by age or text genre possible? No
  6. number of grammatical sentences: Yes
  7. number of words: Yes
  8. number of unknown words, hard words, depending on the readability formula: not in the supported readability formulas
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: Yes
  11. Interpretation of the results: Yes
  12. Errors: nothing found, but some results seem to be rounded
  13. remarks: You have to sign-in to perform a areadability analysis, it's free. All your texts are stored, there is no information what may happen to your texts. There is also a lexical density test. Autocrit has interacting tools and compares your text with other authors or text genres. The newer version of Dale-Chall and Spache are not available in the basic free ersion. You have to register to use the basic functions. All advanced features must be paid with reasonalable prices. Files must contain at least 200 words.
CefrLex

website: CefrLex
formulas supported: no readability formulas
results: contains common words for 2nd language learners in different languages; all words of the text are classified in levels from A1 to C1
output: language level of each words of the text
remarks: the output is very impressing and useful

Character Calculator (CC)

website: Character Calculator (CC)
author/organization: Burak Özdemir 

  1. Which formulas are used in the analyses? Flesch reading ease, Flesch-Kincade grade, SMOG, Gunning Fog, Dale-Chall
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: no (for Dale-Chall)
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: not all correct
  11. Interpretation of the results: yes
  12. remarks: Character counter counts more than words, sentences, and paragraphs. If you open the menu (left top), readability formulas are available.
    The values and their interpreation are shown. It is not clear, which version of Dale-Chall is used. The implications of the readability formulas are discussed at the bottom of the page.
    The design is somehow cumbersome, you have to enter your text several times depending on what you do. Also some menu items appear twice. More annoying, some modules count different in the word calculator and the readability section.  The number of syllables is not correct: 367 instead of 369. The values of the readability formulas always have two decimal places and are uniform.
    Flesch's Reading Ease Index slightly differs (65,08 instead of 64,46), the value of Dale-Chall does differ a lot (14,47 instead of 32,66). 
    Only one test at a time. Caveat: Remove blanks at the end of lines / end of file. The value for Flesch-Kincaid seems to be the value for Flesch Reading Ease, however, also the reading age is computed. The syllable counter module also counts sentences, whereas the number of sentences is infuenced by empty lines (e.g. CRCR). Also blanks are counted as characters.
    Also readability formulas for Spanish texts are available: Fernández-Huerta, Szigriszt-Pazos, INFLESZ, Gutiérrez de Polini and Legibilidad Mu.The input data are stored on US servers, the website is operated from Turkey, the data are deleted after one week.  
CheckReadability

website: CheckReadability
organization: no imprint

  1. Which formulas are used in the analyses? ARI, Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, Smog, Coleman-Liau, Linsear Write, Forcast, new Dale-Chall
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes, problems: first version counted 11 instead of 10 sentences
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: yes
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: mostly correct
  11. Interpretation of the results: yes
  12. remarks: All formuals are given with the values of the text, also the limitations and implications for each formula are described in detail. It counts 11 sentences instead of 10, also the number of syllables is smaller than the number (367 instead of 369 syllables). The number of complex words is correct, also the values for Fog. The results of all other readability formulas differ from the correct values, due to the counting of sentences and syllables. Some formulas were not standardized, so the results are underestimating the difficulty of the text: the results for SMOG and Linsear write. No information on the owner of the website or if data are stored or passed to other companies.
Datayze

website: Datayze
organization: Sarah K. Tyler

  1. Which formulas are used in the analyses?  Flesch Reading Ease, Gunning Fog, Flesch-Kincaid, SMOG, Dale-Chal (which one?)l, Fry readability grade level
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste, file
  4. Are subanalyses (e.g. paragraph) possible? yes, by paragraph
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: no
  8. number of unknown words, hard words, depending on the readability formula: no, but percentage of unknown words for Dale-Chall
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: mostly correct
  11. Interpretation of the results: yes, in separate pop-up windows
  12. remarks: Datazye has a detailed user interface that shows you what the results will be. It also allows the analyses of chapters and the whole text. It is also possible to sort the results by the values of the readability formulas and save them to a file. The implications of readability formulas are described. The paragraphs are detected automatically if a line ends which can lead to too many paragraphs. After reformatting the text the results did change. Obviously every end of line (EOL) is regarded as the end of a sentence. Abbrevations like Prof. or Dr. were tackled correctly (no end of sentence point). The results for the number of words, number of syllables and number of difficult words are not shown. The value for Flesch-Kincaid is correct, the ones for Flesch's Reading Ease and Fog are a little bit too high. The version of the Dale-Chall formula is not mentioned, it seems to be the value of reading age, the interpretation of the results is poor. User data stored up to one year, but not given away. Minimum file size 30 sentences, not standardized.
Editpad

website: Editpad
author/organization: no imprint

  1. Which formulas are used in the analyses? Flesch-Kincaid Reading Ease and grade level, Coleman-Liau, Ari
  2. Are the implications of each readabilty formula explained?
  3. Which parts of the text are analyzed? copy & paste, file
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes, different values depending on the module used
  8. number of unknown words, hard words, depending on the readability formula
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: incorrect for syllable based readability formulas
  11. Interpretation of the results: very poor
  12. remarks:Editpad offers the results of readability formulas and a lot of other tools like plagiarism checker, paraphrasing tool or story generator. You can cut and paste the text into a window or load a file. The number of words do differ: the gettysburg text has 272 words and 276 words in the results table. The longest sentence is shown. The formulas and their implications are explained, the interpretation consist of one word only - average. The website has no imprint, contact is only possible via contact form or e-mail.
Good calculators

website: Good calculators
author/organization: John Sanders & Andrew Stacy

  1. Which formulas are used in the analyses? Flesch Reading Ease und Flesch-Kincaid
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: incorrect
  11. Interpretation of the results: yes
  12. remarks: Good calculators offers a lot of calculators, some for calculating readability formulas: Flesch Reading Ease und Flesch-Kincaid. The results are explained. The number of words and sentences are given, the number of syllables not. The implications of the formulas are not mentioned explicitly.
Gorby

website: Gorby
author/organization: no imprint

  1. Which formulas are used in the analyses? ARI, Coleman-Liau, Dale-Chall, Flesch Reading Ease, Flesch-Kincaid, Smog, Gunning Fog, Spache (which version?)
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste, saving files also possible
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences:  yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: yes
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: incorrect except Smog but syllable counting has many errors, e.g. words like quarter, hopeful, Cleveland, equal, widely are counted as words with more than 2 syllables, where as words like remaining or studying are not counted in this case.
  11. Interpretation of the results: mostly correct and/or similar close
  12. remarks: Use the left menu to find the readability scores, all formulas are explained and all values inserted so one can see which values where used for the computation. Difficult words are shown also within the complete text. However, it is not clear which versions of Dale-Chall and Spache were used. You have to install a kind of desktop app separate from your browser as a so called Progressive Web App that is not supported e.g. by Firefox.However, the results are calculated and explained. In the free version the results of ARI, Dale-Chall, Flesch-Kincaid, Coleman-Liau, Flesch Reading Ease, and Gunning FOG are shown. If you find yourself through the menu, you get a lot of information about the implications of each readability formula.  
infyways

website: infyways
author/organization: Infyways Solutions Private Limited 223,224 DLF Cyber City, Bhubaneswar 

  1. Which formulas are used in the analyses? Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, ARI, Linsear Write
  2. Are the implications of each readabilty formula explained? no
  3. Which parts of the text are analyzed? copy & paste, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: yes, but incorrect
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: Smog is correct, all others are incorrect
  11. Interpretation of the results: no
  12. remarks: The same company offers another tool named Text Analyzer Tool. Tests whow that both programs differ in number of letters and sentences. Infysys only gives the results of the readability formulas and the interpretation. It is also possible to check a webpage.
Juicy Studios online readability tester

website: Juicy Studios online readability tester
author/organization: no imprint

  1. Which formulas are used in the analyses? Gunning Fog, Flesch Reading Ease, Flesch-Kincaid
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text:  URL only
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: incorrect
  11. Interpretation of the results: yes
  12. remarks: Words with 1, 2, 3, 4 and more syllables,  % of words with 3 syllables and more are counted. You can test your own text if it is on a webpage, it is not possible to cut and paste some text. The site redirets you to Webfx. The sample texts were copied to a website, so a test was possible. The site seems to be outdated, dates are from 2013 although the copyright notice says 2000-2025.
myessaywriter.ai

website: myessaywriter.ai
author/organization: Sharjah, United Arab Emirates

  1. Which formulas are used in the analyses? Flesch-Kincaid, Gunning Fog, Smog, Ari, Coleman-Liau
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, file text, file, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? yes, by age group
  6. number of grammatical sentences:
  7. number of words:
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: 
  10. results of the appropriate readability formulas: test limit of 150 words
  11. Interpretation of the results:
  12. remarks: There is a limit of 150 words, and you have to buy a plan first. Nice: Selection of the readability formulas by age of the recipients. However, you can seelect children as an age group, but readability formulas like Dale-Chall or Spache are not implemented. Your data are encrypted and never passed to third parties. But: it wants access to your clipboard.
Online-utility.org

website: Online-utility.org
author/organization:

  1. Which formulas are used in the analyses? Flesch-Kincaid, Gunning Fog, Smog, Ari, Coleman-Liau
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? yes, by age group
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: test limit of 150 words
  11. Interpretation of the results: 
  12. remarks:
Originality.ai
Originality.ai
author/organization: Collingwood, Ontario, Canada L9Y 2L6
  1. Which formulas are used in the analyses? Flesch Kincaid Reading Ease and Grade Level, ARI, Coleman-Liau, Gunning Fog, SMOG, Power, Sumner, Kearl, Forcast, Dale-Chall, Spache, Linsear Write
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, file, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: no
  7. number of words: no
  8. number of unknown words, hard words, depending on the readability formula: no
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: only Flesch Reading Ease, all others were hidden.
  11. Interpretation of the results: no
  12. remarks: You cannot test the program without sign-up. Linsear Write is not standardized nor explained, no definition of difficult words, which versions of Dale-Chall and Spache were used.
Prepostseo

website: Prepostseo
author/organization: Enzipe Software House, Faisalabad, Pakistan

  1. Which formulas are used in the analyses? Flesch Kincaid Reading Ease and Grade Level, ARI, Coleman-Liau
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, file, URL, *.doc, *.docx, *.pdf file formats supported
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: yes, but false
  10. results of the appropriate readability formulas: only ARI is correct
  11. Interpretation of the results: 
  12. remarks: limit 5000 words. the keywords are not defined, nice text metrics and collocatinos containing two or three words.
Readable.com

website: Readable.com
author/organization: Added Bytes Ltd, Hassocks, UK

  1. Which formulas are used in the analyses? Flesch Reading Ease, Flesch-Kincaid, Gunning Fog in the free online version, many more in the full version but only for English texts: Smog, Ari, Spache (version not mentioned), new Dale-Chall, Powers-Sumner-Kearl, Raygor readability graph, Fry Readability graph, IELTS, CEFR, Lix, Rix, Forcast, Lensear Write (it is not misspelled)
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: not available yet, because you have sos sign-up to use the program
  4. Are subanalyses (e.g. paragraph) possible?
  5. Is a selection by age or text genre possible?
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula
  9. number of syllables if readability formulas use them
  10. results of the appropriate readability formulas
  11. Interpretation of the results
  12. remarks: The export requires a trial vesion (free for 7 days), results are exported in CSV and PDF format, text can be exported in word, open document, pdf, html, latex. The are also word analyzers for different word lists so one can see the known words: Dale-Chall, Dolch, Ogden, Spache and Fry. The full version has even more readability formulas. The company also offers an API that returns the results. In total: a nice website that has lots to offer.
Readablility.ch

website: Readablility.ch
author/organization: Christian Bachmann and Roger Gösele

  1. Which formulas are used in the analyses? Flesch Reading Ease, Flesch/Kincaid, FOG, SMOG, LIX; German: Amstad, WSTF - which one?; French: Kandel & Moles; Italian: Gulpease; Spanish: Flesch-Szigriszt / INFLESZ ; Dutch: Flesch-Douma
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: close to the correct values, but more than rounding errors.
  11. Interpretation of the results: yes including the readability formulas
  12. remarks: You select the language of the text, and the appropriate formulas are shown. The text parts are shown in different colours depending how easy these are to understand.
ReadabilityFormula

website: ReadabilityFormula
author/organization:  Brian Scott, MicroPower & Light Co. 

  1. Which formulas are used in the analyses? Flesch-Kincaid, Ari, Coleman-Liau, Flesch Reading Ease, Gunning fog, Smog, Linsear write, Forcast, Fry Graph, Raygor graph, new Dale-Chall, Fry Sight, Spache
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, file
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? yes, many options text genres and type of audience
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula
  9. number of syllables if readability formulas use them: yes
  10. results of the appropriate readability formulas: 
  11. Interpretation of the results
  12. remarks: All values are inserted so one check the calculation, options are available for sentence count, inflected words, compound words, proper nouns (familiar/unfamiliar), handle numbers, URLs, e-mail addresses.  Many formulas and useful options, the output shows many details how to check the validity of the results. Also text metrics give a lot of explanation, although many of these are not explained, e.g. long sentences, hard adjectives etc. These are shown in extra tabs.
Sitechecker

website: Sitechecker
author/organization: Cyber Circus Limited, Gibraltar

  1. Which formulas are used in the analyses? Gunning Fog, Flesch Reading Ease
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes, but one too many
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: incorrect
  11. Interpretation of the results:yes
  12. remarks: A quick and easy to use tool, but only two formulas with false results.
STORYToolz

website: STORYToolz
author/organization: Chuck Heintzelmann

  1. Which formulas are used in the analyses? Flesch-Kincaid, ARU, Coleman-Liau, Flesch Reading Ease, Lix, Smog
  2. Are the implications of each readabilty formula explained? no
  3. Sources of text: copy & paste, limit 5K
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: incorrect
  11. Interpretation of the results: no
  12. remarks: You can analyse up to 5120 words. Output can be exported as PDF, Excel, or CSV file.
WebFx

website: WebFx
organization: WebFX Harrisburg, PA, 17102, USA

  1. Which formulas are used in the analyses? Flesch-Kincaid, Gunning, Coleman Liau, ARI, and SMOG
  2. Are the implications of each readabilty formula explained? yes
  3. Sources of text: copy & paste, URL
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: not necessary
  9. number of syllables if readability formulas use them: no
  10. results of the appropriate readability formulas: Flesch Kincaid and Coleman-Liau are correct, the others are incorrect
  11. Interpretation of the results: yes
  12. remarks: This is a nice and easy to use tool with some goodies. You can enter a text from the clipboard, a file name (HTML will be stripped). WebFx may share users’ data with TeamAI.
Wrise free readability checker

website: Wrise free readability checker
author/organization: Rob Truslove, Wrise, Bury, UK

  1. Which formulas are used in the analyses? Flesch-Kincaid, Flesch Reading Ease, Gunning Fog, SMOG, Dale-Chall Fry Readability grade
  2. Are the implications of each readabilty formula explained?
  3. Sources of text: copy & paste
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes
  8. number of unknown words, hard words, depending on the readability formula: no, only percentage of unknown words for Dale-Chall
  9. number of syllables if readability formulas use them: not necessary
  10. results of the appropriate readability formulas: correct
  11. Interpretation of the results
  12. remarks: This tool is very fast and has a nice dsign. The version of Dale-Chall is not mentioned.
 
Wordcalc

website: Wordcalc
author/organization:

  1. Which formulas are used in the analyses? Flesch-Kincaid Reading Ease, Gunning Fog, Coleman-Liau, SMOG, ARI, New Dale Chall , Spache (which one?)
  2. Are the implications of each readabilty formula explained? yes
  3. Which parts of the text are analyzed? text
  4. Are subanalyses (e.g. paragraph) possible? no
  5. Is a selection by age or text genre possible? no
  6. number of grammatical sentences: yes
  7. number of words: yes, but incorrect
  8. number of unknown words, hard words, depending on the readability formula: no
  9. number of syllables if readability formulas use them
  10. results of the appropriate readability formulas
  11. Interpretation of the results
  12. remarks:
remarks: Another easy to use tool that also explains the formulas itself and how to interpret the results. Also a syllable counter is offered, but this often counts one syllable too many. Also abbrevations points are not considered. If this algorithm is really used by the readability checker, your results may be biased.

Excluded software - under construction

The lists that are the basis of this section are SEO tools, and not all links use readability formulas for SEO purposes. Programs were excluded if there is no online tool available, or if only one formula is used. The following list includes the links and the reasons why these programs were excluded. 

Cathoven Readability Checker Cathoven analyzes text up to 250 words only, and a registration is required, but this failed. Mails to the support were not answered. 

Copywritely Flesch-Kincaid only, therefore excluded

Ginger Writing Assitant no online tool to check a text with readability formulas

GoWinston.ai doesn't work und returns an error message. Disabling the ad-blocker didn't help. Also using other browsers (Firefox, Edge, Vivaldi and Opera) didn't fix the problem.

Grammarly Flesch reading ease only. User data may be used for internal and external purposes therefore not included may retain random samples of de-identified text to help us improve the algorithms underlying our software and services” but “do not share the texts that you check with Grammarly with any third parties” and “have not sold, do not sell, and will not sell customer data”

Gunning Fog  calculator offers only one readability formula.  

Health Literacy Editor only offers UK grade (Flesch-Kincaid?). It calculates the UK grade, whatever this is. Complex and long words (4 syllables and more), complex sentences and sentences with passive voice are shown in different colours. Unfortunately they are not counted. It also remains unclear what complex words are, the explanation given is that these words can be substitutrd by easier words.

Hemingway only offers Flesch-Kincaid.

Junia.ai tries to improve the readability uses Flesch reading ease, no online tool to check a text with readability formulas.

Language Tool no online tool to check a text with readability formulas, verifies facts using AI for many languages

Links Assistant no online tool to check a text with readability formulas

Longshot AI no online tool to check a text with readability formulas

NHS Medical Document Readability Tool calculates Flesch-Kincaid only, the results was incorrect.

Okapi The online tool has a limit of 200 words. The connection to the internet is insecure. Only new Dale-chall and Spache readability formulas are im0plemented, and you select one formula from a menu dependent of the age of the readers (children).

Outwrite only afte registration you can evalute what this tool is usefule for. It seems that readability formulas are also used, but there is no further information which ones.

Searchmetrics (Conductor) no online tool to check a text with readability formulas

Spanishreadability.com is no longer available.

Surfer SEO no online tool to check a text with readability formulas

ProWritingAid no online tool to check a text with readability formulas, but tools for avoiding complex sentences or passive voice, style inconsistency checks, sentence length analysis, word choice suggestions.

Readability analyzer no online tool to check a text with readability formulas. However, you can download a*.zip file.

Readability pro the results show the grades, but not the values of each formula for Flesch-Kincaid, Gunning fog, SMOG.

Textinspector  does not provide readability formulas but a lot of text metrics e.g. academic words percentage, Percentage of words at B1 CEFR level There is a limit of 250 words for guests, if you have bigger text you have to pay. The most expensive plan allows files up to 13,000 words only. The data are cleared from the server after 6 hours. The company also offers the use of an API.

Voyant Tools are included because the readability formula used is not named, and there are not many text metrics available. It generates word lists, phrases, collocations, word grapes, word density. All words are in lower case, the following languages are supported; Arabic, Bosnian, Croatian, Czech, English, French, German, Hebrew, Italian, Japanene, Portuguese, Russian, Serbian, Spanish.