There was an interesting idea in the post I stumbled across last week that the readability level may affect your rankings because…
from a logical standpoint, having reading level as a ranking factor among the search engines just makes sense. It’s a good way to match the right content with the right audience.
I never did any testing to confirm that, nor was readability check ever part of my SEO process but it does make sense. So in case you ever need to find out how readable your content is, let me offer you a one-stop overview of readability level checkers and comparison tools.
Readability Level Tests
| Readability test name | Parameters to take into account | The score corresponds to… |
| Flesch–Kincaid readability test | total words versus total sentences; total syllables versus total words | U.S. grade level |
| Coleman-Liau Index | Characters versus words; Sentences versus words | U.S. grade level |
| Automated Readability Index | characters per word; words per sentence | U.S. grade level |
| Gunning fog index | words per sentence; complex word per total number of words (complex = words with three or more syllables with some exceptions like proper names or words with common suffixes -es, ed, etc) | U.S. grade level |
| SMOG | Number of polysyllables (three or more syllables excluding proper names) versus number of sentences | years of education needed to completely understand a piece of writing |
A handy tip: if you are not in the USA (like myself) and it takes some serious effort to translate the US grade system, U.S. grade level 1 corresponds to age 6, and in general adding 5 to the grade level gives an estimate of the typical reader’s age.
The page I was playing with to try readability level checkers: NYTimes article. So let’s take a look at readability tools:
Free Readability Level Checking Tools
| Readability tool | Type | Readability test(s) the tool is based on | Parameters taken into account | Issues |
| Fog | online | Gunning fog index | Number of words, number of sentences | Includes proper names |
| SMOG | online | SMOG test | Number of polysyllables, number of sentences | - |
| Flesh | desktop | Flesch–Kincaid readability test | total words versus total sentences; total syllables versus total words | - |
| Readability score | online | Flesch-Kincaid Grade Level, Gunning-Fog Score, Coleman-Liau Index, SMOG Index, Automated Readability Index | - | - |
| Edit Central | online | Flesch reading ease score, Automated readability index, Flesch-Kincaid grade level, Coleman-Liau index, Gunning fog index, SMOG index | - | - |
| Read-able | online | Flesch reading ease score, Automated readability index, Flesch-Kincaid grade level, Coleman-Liau index, Gunning fog index, SMOG index | - | Includes proper names |
| Online readability test | online | Coleman Liau index, Flesh Kincaid Grade level, ARI (Automated Readability Index), SMOG |
- | - |
| uicy Studio Readability Test | online | - | - |
[I described some of the tools in more detail below]
Fog
Fog tool (as the name suggests) uses Gunning fog index to calculate the text reading level. The best things about the tool are:
- It highlights the “complex” words (those that have more than 3 syllables in blue);
- Marks separate sentences.
This looks really useful for visualizing “difficult” spots in your text to make it clear if you need any edits:
Readability score
Readability score is a nice way to compare all the listed readability tests (Flesch-Kincaid Grade Level, Gunning-Fog Score, Coleman-Liau Index, SMOG Index, Automated Readability Index):
Edit Central
Edit Central is another handy tool that compares a number of readability tests, shows useful stats and also underlines complex words:
Juicy Studio Readability Test
Juicy Studio Readability Test displays some really useful page copy stats including average length of a sentence, complex words, etc:
Further reading and sources:
I’ve been reading your articles for quite a while now and this is your best post yet – it’s something I’ve never considered before opens up an exciting new area to ensure the usability of sites (regardless of whether it helps with SEO or not)
That is quite amazing research done by you, as usual you rocks with very useful information. This is very helpful for content writers or technical writers SEO’s & website analyzers
Thanks for the readability tools.
-Bryan
Thank you for the great article! I really enjoyed your readability tools reviews. Very interesting stuff!
very interesting, and really the way u present is awesome ….. thanks
great post for me refer my clients to. Especially the ones who deal in technical language and acronyms that are beyond comprehension (actually, I’m guilty of that myself!) will see quite clearly how difficult it can be to communicate clearly with new prospects who may not be as insider-savvy on the language.
Thanks!
Nice post. Thanks for including my tool in your post. I’d be interested in how you think http://www.read-able.com/ could be improved.
It measures 6 of the most popular readability indices as well as:
* No. of sentences / words / complex words
* Percent of complex words
* Average words per sentence / syllables per word
I’m always interested in ways that it can be improved, different indices that can be added.
We were just researching this and ran across your blog post. Thanks for the overview of these tools. there is the Scribe tool for Thesis theme on WordPress that analyzes readability in context with SEO, but it is a bit on the expensive side. The readability index is built into Google Docs as well and that is free.
Great info – thanks.
One thing I would like to see (to help me with a course I am writing) is a direct comparison between Gunning Fog and Flesch-Kincaid grades, i.e., I can see from your test above that Gunning Fog = 9.5, while Flesch Kincaid = 7.7 but is there a 'Conversion Table' somewhere like Centigrade / Farenheit, or does it not work like that?
Great info – thanks.
One thing I would like to see (to help me with a course I am writing) is a direct comparison between Gunning Fog and Flesch-Kincaid grades, i.e., I can see from your test above that Gunning Fog = 9.5, while Flesch Kincaid = 7.7 but is there a 'Conversion Table' somewhere like Centigrade / Farenheit, or does it not work like that?