Readability and SEO: What Your Score Means and How to Fix It

Does readability affect SEO?

Not directly, as far as Google has documented it. Google never mentions a readability score or the Flesch formulas in its Search Central documentation. It does say, in plain words, that good content is easy to read, well organized and free of mistakes. Readability matters because readers matter, not because a score is computed somewhere.

A lot of SEO plugins show a readability grade next to the keyword grade, in the same green, orange or red. That presentation suggests both are ranking inputs. Google documents neither score.

Here is what Google actually writes. In its SEO Starter Guide, under “Make your site interesting and useful”, the first attribute of compelling and useful content is this:

The text is easy-to-read and well organized: Write content naturally and make sure the content is well written, easy to follow, and free of spelling and grammatical mistakes. Break up long content into paragraphs and sections, and provide headings to help users navigate your pages.

Google Search Central, SEO Starter Guide

The same guide says that creating content people find compelling and useful “will likely influence your website’s presence in search results more than any of the other suggestions in this guide.” And in its page on helpful, people-first content, Google asks two questions that touch on writing quality: “Does the content have any spelling or stylistic issues?” and “Is the content produced well, or does it appear sloppy or hastily produced?”

What Google says vs. what is inference

The honest way to put it is in two columns: what you can quote, and what you are deducing.

What Google documents	What is inference, not documentation
Good content is “easy-to-read and well organized”	That Google computes a Flesch score for your page
Break long content into paragraphs, sections and headings	That a higher score means a higher ranking
Check for “spelling or stylistic issues”	That there is a target score Google prefers
”The length of the content alone doesn’t matter for ranking purposes”	That a readability plugin’s green light protects you
Focus on people-first content	That readable pages perform better because readers stay and come back

The last line on the right is a reasonable bet. But it is a bet: Google does not publish how reader behavior feeds into its systems, and we will not pretend otherwise. A readable page is not rewarded for being readable. It is simply easier for a reader to get what they came for, which is what Google says it tries to reward.

One more data point, older but often cited for a reason. In 1997, the Nielsen Norman Group studied how people read web pages and summed up the answer in two words: “They don’t.” In their tests, 79 percent of users always scanned any new page; only 16 percent read word by word. Their advice: meaningful subheadings, one idea per paragraph, the conclusion first. Those habits still apply.

What does the Flesch Reading Ease score measure?

Two things only: how long your sentences are, in words, and how long your words are, in syllables. It knows nothing about meaning, order, jargon or whether your answer is right.

The formula, published by Rudolf Flesch in 1948, as given in the Wikipedia article on the Flesch–Kincaid tests:

206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)

Read it as: start at about 207, lose a point for every word you add to the average sentence, and lose a lot more for every extra syllable in the average word. The higher the result, the easier the text. On normal prose it lands between 0 and 100, but it has no theoretical floor: a string of long technical words can push it below zero.

The usual interpretation table looks like this:

Score	US school level	Meaning
90–100	5th grade	Very easy
80–90	6th grade	Easy, conversational
70–80	7th grade	Fairly easy
60–70	8th–9th grade	Plain English
50–60	10th–12th grade	Fairly difficult
30–50	College	Difficult
10–30	College graduate	Very difficult
0–10	Professional	Extremely difficult

And the Flesch-Kincaid grade level?

It uses the same two ratios, weighted differently, and translates the result into a US school grade. It was developed in 1975 by J. Peter Kincaid and his team under contract to the US Navy.

0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59

A grade of 8 means an eighth grader should follow the text. Because the two formulas weight sentence length and word length differently, the reading ease score and the grade level are not directly convertible: long words hurt the reading ease score much more than they raise the grade.

The same Wikipedia article notes the main limits. The formulas were built for school books. They ignore differences between readers, as well as layout and content. And they are easy to game: very short, choppy sentences raise the score without making anything clearer.

Does it work in French?

Not as is. The original formula and its interpretation table were built for English texts, and the weights it gives to sentence length and syllables do not carry over to another language.

In 1958, L. Kandel and A. Moles published an adaptation, “Application de l’indice de Flesch à la langue française”. A 2022 paper from Université Laval gives it as 207 − 1.015 × (average sentence length) − 0.736 × (syllables per 100 words): the sentence term is unchanged, the syllable term is lighter. The authors also found a clear progression of scores from simple to complex texts, but “too much overlap between levels to reliably classify a document in one category based on that information alone.”

That is a useful caution for any language. The readability analyzer applies the Kandel and Moles constants on its French version, and shows the grade level for French only as an order of magnitude.

What readability score should you aim for?

For a general web audience, aim for a Flesch Reading Ease of roughly 60 to 70, the band the standard table calls plain English. That is a sensible working target, not a number Google asked for.

Three adjustments matter more than the exact figure:

• Match your reader. A tax adviser writing for accountants can sit at 40 without a problem. The same text sent to first-time founders will lose them. Compare yourself to the pages that rank for the query, not to an abstract target.
• Compare versions, not pages. The score is most reliable as a before/after on the same text. If your edit moved it from 38 to 55, you removed real friction. Whether 55 is “good” depends on the topic.
• Watch the long sentences more than the average. An article averaging 16 words per sentence can still hide a dozen sentences of 40 words. That is where readers drop off.

For the sentence threshold, GOV.UK’s guidance is concrete: “Try to split up sentences that are over 25 words long.” It is also the threshold the readability analyzer uses when it counts long sentences and quotes the three longest.

How do you improve readability? A four-step editing method

Fix the structure first, then the sentences, then the words. Most of the score moves with sentence length, and most of the reader’s comfort comes from finding the answer quickly.

1. Put the answer first

Each section should open with the answer to the question in its heading, in one or two sentences. Details, nuance and examples come after. It is the inverted pyramid the Nielsen Norman Group recommended in 1997, and Digital.gov’s Clear and short page says the same for paragraphs: “Each paragraph should start with a topic sentence.”

Before:

How often to publish on a company blog has been the subject of a lot of debate over the years, and many site owners are unsure how many articles they should put out each month, especially when they hear very different numbers from different experts.

After:

Publish only as often as you can review each article properly. A pace you can keep beats a number someone else picked.

The first version spends 45 words and never answers. The second answers in its first sentence.

2. One idea per sentence

Digital.gov puts it plainly: “Express only one idea in each sentence.” Sentences loaded with clauses and exceptions, it adds, “confuse the audience and lose the main point.” Splitting is the fastest way to raise a Flesch score, because sentence length is half the formula.

Before (45 words):

In order to make sure that the articles published on your website can be understood by as many visitors as possible, it is recommended that sentence length be reviewed before each article goes live, since long sentences are harder to follow on a phone screen.

After (two sentences, 26 words in total):

Check sentence length before each article goes live. Long sentences are harder to follow, especially on a phone, and you want every visitor to understand you.

Nothing was lost. “In order to make sure that” became nothing, “it is recommended that” became a verb, and the reason became its own sentence.

3. Prefer the active voice

GOV.UK’s Use clear language guidance explains why:

The active voice is more direct and puts the focus on the user and the action they need to take. It also keeps sentences short. In contrast, the passive voice results in long sentences and can make the content harder to read.

GOV.UK, Use clear language

Digital.gov adds a test: passive sentences usually combine a form of “to be” with a past participle, and they “often do not identify who is performing the action.”

Before:

The pricing page was updated and the new plans were announced to existing customers.

After:

We updated the pricing page and emailed the new plans to every existing customer.

The active version tells the reader who acted and how. Passive voice is not banned: GOV.UK itself notes it can work when the outcome matters more than who acted. Count it, then keep only the ones that earn their place.

4. Shorten the words that do not need to be long

GOV.UK warns that “Words ending in ‘–ion’ and ‘–ment’ tend to make sentences longer and more complicated than they need to be.” Those nouns usually hide a verb.

Before:

The implementation of an optimization of your title tags will result in an improvement in click-through rate.

After:

Rewrite your title tags and more people may click.

Notice the “may”: the edit made the sentence shorter, and also more honest. Long, abstract phrasing often hides an overpromise.

Keep the technical term when it is the right one. GOV.UK says it plainly: “Where you need to use specialist terms, you can.” Explain it in plain words the first time it appears, then use it.

Then structure the page

Readability is not only sentences. Google’s own advice is to break up long content into paragraphs and sections with headings. GOV.UK suggests “no more than 5 sentences” per paragraph. Digital.gov sets an outer limit: “Paragraphs should never be longer than 250 words.” Use lists for steps and options, a table when you compare, and bold for the few words a scanning reader must not miss.

How to use a readability analyzer without being fooled by it

Use it as a highlighter, not a judge. The score tells you where the long sentences and long words are; you decide whether they belong.

A practical routine:

1. Paste the draft into the free readability analyzer. Everything runs in your browser.
2. Look first at the share of sentences over 25 words and at the three longest sentences it quotes. Fix those before anything else.
3. Check the passive sentences it counts. The detection reads the pattern of the words, so it can miss some and flag others wrongly.
4. Re-run it. Compare the score with the first draft, not with an ideal.
5. Check length separately with the word counter, and remember that Google says length alone does not matter for ranking.

Two traps. First, chasing the score with very short sentences: the result reads like a telegram, and the formula rewards it anyway. Second, swapping precise words for vague ones to save syllables: “use” is better than “utilize”, but “mortgage” is better than “home loan thing”. The Flesch formulas cannot tell those apart; your reader can.

Readability and AI-written drafts

AI drafts are usually grammatical and often readable on paper. Their typical problems are elsewhere: an introduction that circles the topic before answering, and long sentences stacked with qualifiers. The four-step method above fixes both, and it fits inside the human review that Google expects for AI content, as the guide AI content and Google explains.

Answer-first sections also help on the AI search side: an assistant that quotes your page needs a passage that answers on its own. The guide GEO: get cited by ChatGPT, Gemini and Grok covers what is documented there.

The short version

Readability is not a documented ranking factor, and no Flesch score will rank a page that does not answer the query. But Google tells you, in so many words, to write text that is easy to read and well organized, and readers leave pages they cannot follow. Answer first, one idea per sentence, active voice, shorter words where they fit. Then check your work with the readability analyzer, and treat the score as a before/after on your own draft.