Readability scores: Are they really helping SEO or just a myth?
Should you care about readability scores like Flesch Reading Ease (FRE) or Flesch-Kincaid Grade Level (FKGL)?
by Narmina Balabayli
A readability score is a numeric measure that estimates how easy a piece of text is to read and understand.
Readability score is significantly more helpful for securing AI citations than it is for achieving rankings on the SERP.
You can rank on the first page of Google with a "difficult" or "bad" readability score if your content is comprehensive and authoritative.
You are more likely to be quoted by an AI chatbot if your writing is simple, clear, and easy to parse.
For AI citations, aim for a Flesch Reading Ease (FRE) score of 60–70, which is considered plain English and easy for most readers to understand. For Flesch–Kincaid Grade Level (FKGL), target around 7–8, as it keeps content accessible to a broad audience.
What are readability scores? Do readability scores like Flesch Reading Ease (FRE) or Flesch–Kincaid Grade Level (FKGL) really help SEO? What do they mean by “readability’s effect on SEO”? Do they mean direct rankings, or something else?
If you search readability scores on Google, you'll see titles say things like “Readability’s effect on SEO,” “readability and SEO,” and “the importance of readability for SEO ranking,” etc.
These phrases and questions use presuppositional framing, which can mislead and confuse readers. So, I thought I’d write about it.
What are readability scores?
A readability score is a math formula that measures how easy a text is to read. The tools that measure the readability scores look at two main things: how long your sentences are and how many syllables are in your words.
There are many types of readability scores, each aiming to estimate how easy or hard a text is to understand, but their usage contexts can differ:
Flesch Reading Ease (FRE): measures how easy a text is to read on a scale from 0 to 100
Flesch-Kincaid Grade Level (FKGL): represents the number of years of education generally required to understand the text.
Gunning Fog Index: estimates the number of years of formal education required to understand a text. Commonly used for business and technical writing.
SMOG Index (Simple Measure of Gobbledygook): commonly used in healthcare to ensure patient information is accessible.
Automated Readability Index (ARI): determine the U.S. grade level required to comprehend English text.
Coleman-Liau Index: estimate the U.S. grade level required to understand a text by measuring the number of characters and sentences per 100 words.
Dale-Chall formula: assess text comprehension difficulty based on sentence length and vocabulary familiarity.
Currently, Flesch Reading Ease (FRE) and Flesch–Kincaid Grade Level (FKGL) are the big names because they fit most types of web content, which is why their readability tests are used the most and often discussed in SEO contexts.
Flesch Reading Ease (FRE)
Flesch Reading Ease (FRE) measures how easy a text is to read. This gives you a score from 0 to 100. A high score means the text is very easy to read. A low score means it is very hard. For example, a score of 90 to 100 is great for an 11-year-old. A score of 0 to 30 is best for college graduates.
Flesch-Kincaid Grade Level (FKGL)
Flesch–Kincaid Grade Level (FKGL) estimates the U.S. school grade level needed to understand the text. This test takes the same data but turns it into a U.S. school grade level. For example, if you test the text and you get an 8.0, it means an 8th grader can understand it.
Does a good readability score affect SEO?
Readability, yes. Readability score, no.
You may ask, what's the difference?
Readability does, in fact, have an effect on SEO rankings. However, a good readability score measured by tools has no impact on SEO rankings.
The reason is that the tools we use to measure readability scores don’t “read” content the way we - humans do. They can’t tell whether the text is helpful, offers a unique perspective, or is valuable to a reader, all of which Google prioritizes most.
Google’s John Mueller, have said in '2018 Google Webmaster Hangout' that they don’t use these basic formulas in their ranking systems [found via Search Engine Journal].
Why? Because the formulas are too simple. They can’t tell whether your information is actually good or whether it matches what the user wants. They mainly measure surface-level features like sentence length and the use of short, common words.
However, you should consider your target audience when writing.
Readability scores just tell how easy it is to read and understand the content for the target audience. A score of Flesch Reading Ease 85 doesn’t mean your content is helpful or valuable to a reader.
For example, if you test the FRE or FKGL scores of this following paragraphs, you will see green lights.
“Meta descriptions directly control Google’s algorithm. Adding emojis guarantees page one. My grandma outranks Google by adding keywords.”
But in reality, these sentences are factually wrong, misleading, and completely useless to readers even though they get high readability scores.
Because LLMs tend to prefer text with higher readability scores, it’s easier to see why they sometimes include incorrect information in their answers. They may rely on sources that are easier to process, not necessarily the most correct or authoritative. They can’t always tell whether content was written by experts. In reality, much of the internet is written by everyday people like you and me—and we can be wrong.
Now, let’s understand readability itself.
According to Google, good readability means:
Readers can easily digest the content (e.g., bullet lists make complex sentences easier to read, and visual aids help explain the context, etc.).
Headings are descriptive and easy to skim.
The page loads quickly.
The page provides a good user experience (UX) that supports engagement.
The body text font size is desirably 18px, color is easy to read, is well aligned (left-aligned is usually recommended).
The text has minimal grammar errors.
Sentences are short, ideally fewer than 26 words.
The most important information appears at the start of each paragraph to improve scannability.
Etc.
This is what good readability looks like. Readability is vital because if readers find content difficult to digest, they will likely leave the page (“bounce”), which can signal to search engines that the result wasn’t helpful.
Also, word choice and shorter sentences are especially helpful for a global audience, making content easier to understand for non-native speakers.
Let’s also not forget that while good readability can indirectly benefit SEO by reducing bounce rates and increasing engagement, it doesn’t carry the same weight as content depth, domain authority, or matching search intent.
So, readability (as Google describes it) can affect SEO rankings indirectly, but readability scores themselves are not ranking factors.
Why should you care about readability scores?
Readability scores can help your content earn more AI citations. AI chatbots (like ChatGPT, Perplexity, and Google’s AI Overviews) are more likely to cite and link to pages that are clear and easy to read.
If you want your content to get AI citations, you should aim for a Flesch Reading Ease (FRE) score of 60–70, which is considered plain English and easy for most readers to understand. For the Flesch–Kincaid Grade Level (FKGL), target around 7–8 to keep content accessible to a broad audience.
Note: Of course, readability scores are not the only way to earn AI citations. Content depth is also an important factor in getting cited by AI chatbots.
In short, readability matters for rankings indirectly, but readability scores don’t.
