Readability affects how long visitors stay on your page, how much they share your content, and — indirectly — how well you rank on Google. But what readability score should you actually be targeting? In this guide we break down the main readability formulas, what scores correlate with good SEO performance, and how to optimise your content.
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What Is a Readability Score?
A readability score is a numerical measure of how easy a piece of text is to read and understand. Several formulas exist, each using different variables — most rely on some combination of sentence length, word length and syllable count.
The most commonly used scores in SEO and content marketing are:
- Flesch Reading Ease — scores 0–100; higher = easier
- Flesch-Kincaid Grade Level — US school grade level (e.g. 8 = 8th grade)
- Gunning Fog Index — like FK Grade Level; includes complex word count
- SMOG Index — designed for health and medical content
The Flesch Reading Ease Scale
| Score | Difficulty | Suitable For |
|---|---|---|
| 90–100 | Very Easy | Children's books, basic instructions |
| 70–90 | Easy | Consumer marketing, news articles |
| 60–70 | Standard ✓ Ideal for SEO | Blog posts, web pages, most online content |
| 50–60 | Fairly Difficult | Technical blog posts, industry articles |
| 30–50 | Difficult | Academic papers, white papers |
| 0–30 | Very Difficult | Legal, scientific or highly technical documents |
Best Readability Score for SEO: The Recommendation
For most web content intended to rank on Google, the consensus among SEO professionals is:
- Flesch Reading Ease: 60–70 (standard; 8th–9th grade level)
- Flesch-Kincaid Grade Level: 7–9
- Gunning Fog Index: 8–12
This range represents content that a typical adult can read comfortably without feeling talked down to. It keeps sentences concise, avoids unnecessary jargon, and still conveys expertise.
Does Readability Directly Affect Google Rankings?
Google has not confirmed that readability is a direct ranking signal. However, readability strongly influences the user experience signals that do affect rankings:
- Dwell time / time on page: Easier text keeps people reading longer
- Bounce rate: If your page is hard to read, visitors leave quickly
- Social shares and backlinks: Clear, engaging content earns more links
- Featured snippets: Google tends to favour concise, clear answers for position zero
Yoast SEO, one of the most widely used SEO plugins, includes Flesch Reading Ease in its content analysis precisely because of this indirect relationship with rankings.
Different Content Types, Different Targets
The right readability score depends on your audience and topic:
- Consumer blog posts: 60–70 Flesch (standard)
- E-commerce product pages: 70–80 (easy; short sentences, scannable)
- Technical/developer content: 50–60 (fairly difficult is acceptable)
- Medical/legal content: 30–50 (complexity is unavoidable; use plain language summaries)
- Social media copy: 80–90 (very easy; punchy and direct)
How to Improve Your Readability Score
- Shorten your sentences. Aim for an average sentence length of 15–20 words. Break long sentences at conjunctions like "and", "but" and "because".
- Use simpler words. Replace "utilise" with "use", "commence" with "start", "endeavour" with "try".
- Break up long paragraphs. Keep paragraphs to 3–4 sentences maximum on the web.
- Use subheadings. H2 and H3 headings improve scannability and help readers navigate.
- Use bullet points and numbered lists. They break up dense text and highlight key points.
- Write in active voice. "The team launched the product" reads better than "The product was launched by the team".
- Define technical terms. If you must use jargon, explain it the first time it appears.
The Flesch Formula (For Reference)
If you're curious how Flesch Reading Ease is calculated:
Where ASL = Average Sentence Length (words per sentence) and ASW = Average Syllables per Word.
Lower sentence length and lower syllables per word both increase the score (making text easier). This is why short, common words and shorter sentences score so well.
Frequently Asked Questions
What is the best Flesch readability score for SEO?
A Flesch Reading Ease score of 60–70 is considered ideal for most blog posts and web pages. This equates to roughly 8th–9th grade level and is accessible to the vast majority of adult readers.
Does Google use readability as a ranking factor?
Not directly. Google has not confirmed readability as an explicit ranking factor. However, it strongly influences engagement signals like dwell time and bounce rate, which do affect rankings.
What Gunning Fog index is good for web content?
A Gunning Fog Index of 8–12 is the sweet spot for most web content. Below 8 can feel overly simplistic; above 12 risks losing average readers.