Readability and SEO: Using the Flesch index

1. what is the Flesch Index in terms of readability and SEO?

The Flesch Index was developed to make the readability of texts measurable. It analyzes the average sentence length and the number of syllables per word in order to evaluate the linguistic complexity of a text. The Flesch index is an important factor for readability and SEO. It is calculated using the following formula:

Score = 206.835 – (1.015 × average sentence length) – (84.6 × average number of syllables per word)¹

The following applies:

• Average sentence length = number of words ÷ number of sentences
• Average number of syllables per word = number of syllables ÷ number of words

The higher the value, the easier the text is to read.

Interpretation of the values:

• 90-100: Very easy to understand (e.g. simple children’s books or extremely simple instructions).
• 80-89: Easy to understand (e.g. texts for young people).
• 70-79: Relatively easy to understand (e.g. articles for a broad audience).
• 60-69: Pleasantly readable, suitable for a wide audience.
• 50-59: Moderately difficult to understand (e.g. texts for adults with a higher level of education).
• 30-49: Difficult to read (e.g. academic or technical texts).
• 0-29: Very difficult to understand (e.g. specialist literature, legal or scientific texts).

There are minor adjustments to the formula for the German language, as the sentence structure is often more complex.

Flesch index (German) = 180 – (sentence length × 1) – (proportion of long words × 58.5)

The following applies:

• Sentence length is the number of words per sentence.
• Proportion of long words is the proportion of words with more than 3 syllables, calculated as:
  Proportion of long words = (number of words) / (total number of words)

However, the basic principle remains the same: simple texts achieve higher scores.² Readability and SEO are closely linked. A high Flesch index improves readability and SEO.

2 Why is readability important in online marketing?

The readability of a text influences how users interact with the content. Easy-to-read text ensures that the message is understood clearly and quickly.

1. Longer dwell time: Users stay on the page longer if they can easily grasp the content.³
2. Broader target groups: Easy-to-understand texts appeal to both experts and laypeople and are therefore versatile.⁴
3. Mobile use: Short, well-structured texts are a must, especially on mobile devices. They make reading easier on small screens and reduce frustration. ⁵

3. the connection between the Flesch Index and SEO

The readability of a text has an indirect effect on the ranking in search engines, as it influences important user signals:

• Increase dwell time: Readers stay longer on pages that are formulated in an understandable way. This signals to Google that the content is relevant. ⁶
• Reduce bounce rate: Complex and difficult to understand texts can cause users to leave the page early – a negative signal for search engines.⁷
• More interactions: Comprehensible texts are shared, liked or commented on more often, which additionally increases visibility.⁸
• Mobile-first indexing: Since Google primarily evaluates content based on its mobile display, readable texts on smartphones are a clear advantage.⁹

You can improve your content through targeted readability and SEO measures.

4. tips for improving readability

With these tried-and-tested strategies, you can significantly increase the readability of your content:

1. Use short sentences: Avoid sentence constructions with more than 20 words. They are tiring and make understanding more difficult. ¹⁰
2. Use simple language: Use frequently used words and explain technical terms if they are necessary.¹¹
3. Create a clear structure: Divide the text into paragraphs and use subheadings to increase readability.¹²
4. Incorporate bulleted lists: Lists help readers to grasp information more quickly.¹³
5. Add visual elements: Images, graphics or info boxes break up the text and support the core message.¹⁴
6. Use text analysis tools: Programs such as the Yoast SEO editor or the Hemingway app provide helpful tips for optimizing readability.¹⁵

Consider readability and SEO in your strategy.

Practical example:
A complicated text could read like this:
“The implementation of a consistent SEO strategy requires a detailed analysis of various metric indicators to ensure optimal positioning in search engine results.”

After optimization:
“A successful SEO strategy begins with a precise analysis of important key figures. This way you can ensure that your site ranks well in the search engines.”

The revised version is clearer, more direct and easier to understand. Isn’t it?

5. limits of the Flesch index

The Flesch Index is a valuable tool, but it is not the only measure of text quality. Texts must always fit the context and the target group. In addition, readability should be combined with other SEO measures such as keyword optimization in order to achieve optimal results. ¹⁶

It follows from this: Local SEO and international SEO are influenced by readability, but are only one part of a successful SEO strategy. We will be happy to explain more about this in a free initial consultation. The link between readability and SEO is essential. Readability and SEO are crucial for user satisfaction.

6 Conclusion: Readability and SEO belong together

The Flesch index helps you to improve the readability of your texts, which in turn improves the user experience and thus indirectly increases your search engine ranking. By applying the tips mentioned here, you can create content that impresses both users and search engines. Use effective methods for readability and SEO. By improving readability and SEO, you increase your visibility.

Tip:
Use text analysis tools and optimize your content for your audience. Try it out – the results will be worth it!

Sources

1. Rudolf Flesch, “How to Write Plain English”, Harper & Row, 1979. ↩︎
2. Bamberger, R., & Vanecek, E. (1984). Readability index for German texts. ↩︎
3. Nielsen, J. (2008). Usability and Readability on the Web. Journal of Web Studies. ↩︎
4. Marcus, A., et al (2019). Text Simplification as an SEO Strategy. Language Technology. ↩︎
5. Smith, A. (2020). Mobile Reading Behaviors. Pew Research Center. ↩︎
6. Google Search Central. (2022). Understanding Page Experience. Google. ↩︎
7. Moz (2021). Reducing Bounce Rate for Better SEO. SEO Guide. ↩︎
8. Social Media Today. (2020). How Readability Affects Sharing. Social Media Today. ↩︎
9. Google. (2020). Mobile Indexing Update. Google. ↩︎
10. Plain Language Association. (2017). Principles of Readable Text. Plain Language Association. ↩︎
11. Clear Language Group. (2016). Why Simplicity Matters. Clear Language Group. ↩︎
12. Nielsen, J. (2011). Writing for the Web. Nielsen Norman Group. ↩︎
13. Wroblewski, L. (2015). Text structure and user engagement. In Design for Interaction. ↩︎
14. Interaction Design Foundation. (2019). Visual Content Strategies. Interaction Design Foundation. ↩︎
15. Hemingway App. (2023). Hemingway App Documentation. ↩︎
16. Roth, M., & Keller, S. (2020). Limits of Readability Metrics. Academic Writing Studies. ↩︎