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What is Related Entity Density in SEO and Why Does it Matter?

Published on December 19, 2023 
by Akim Hermoso

Welcome to the dynamic world of SEO! Today, we’re exploring a concept that’s buzzing in digital marketing circles: Related Entity Density (RED). This isn’t just another SEO buzzword; it’s a game-changer. So, what is RED and why is it making waves in the SEO community?

Related Entity Density SEO

Related Entity Density (RED) in SEO is the combination of terms that are closely linked to your main topic. Why does this matter? In today’s SEO landscape, where search engines are getting smarter at picking up context, RED helps your content stand out and resonate with both search engines and real people.

How does RED differ from traditional Keyword Density?

Now, you might be thinking, “Isn’t this just keyword density as a new label?” Not quite. Traditional keyword density is all about the frequency of a single term. RED, on the other hand, is about the variety and relevance of all the keywords that are thematically connected to your main topic. This approach is more in tune with how search engines today process and understand content.


At the heart of RED are three things: your main topic, the related terms, and how often these terms show up in your content. For example, if ‘Digital Marketing’ is your main topic, related terms could be ‘SEO,’ ‘Content Marketing,’ and ‘Analytics.’ The trick is to blend these terms naturally into your content, ensuring they appear frequently enough to create a strong thematic link.

Why is RED crucial for modern SEO?

A high RED score signals that your content isn’t just relevant; it’s a treasure trove of information on the topic. This is crucial as search engines evolve to prioritize content that aligns with what users are really looking for.

Beyond search engines, RED is a champion of user experience. Content that is rich in related terms is more likely to answer different aspects of a user’s query, offering a more fulfilling and comprehensive read. This not only keeps readers engaged but also establishes your content as a go-to resource in its niche.

How can you accurately measure Related Entity Density?

Fortunately, there are several tools at your disposal. SEO software like Moz, SEMrush, and Ahrefs offer features that can help you identify and measure related entities in your content. These tools analyze your text and provide insights into how well it aligns with related terms, giving you a clear picture of your content’s RED.

If you want to go by hand, then yes, manual measurement is possible, though it requires a bit more effort. Start by identifying your main topic and related terms. Then, review your content to count the frequency of these terms. The key is to ensure these terms are used in a way that feels natural and adds value to the reader. While manual measurement might not be as precise as using tools, it offers a hands-on understanding of how related entities are woven into your content.

What are practical examples of RED in different niches?

Let’s take a look at a few topics to fully understand how RED works.

How is RED applied in Digital Marketing Content?

  • In digital marketing, RED involves incorporating terms related to the main topic, like ‘SEO,’ ‘Content Marketing,’ and ‘Social Media Strategies.’ For instance, a piece on SEO might include related terms such as ‘keyword research,’ ‘backlinks,’ and ‘Google algorithms.’ This not only boosts the content’s relevance for search engines but also provides a comprehensive guide for readers interested in SEO.

What does RED look like in niche topics like coffee or taxes?

  • In a niche like coffee, RED would include terms like ‘espresso,’ ‘arabica beans,’ ‘brewing methods,’ and ‘coffee culture.’ For taxes, it might encompass ‘income tax,’ ‘tax deductions,’ ‘IRS regulations,’ and ‘tax planning.’ These related terms help create content that’s not just about coffee or taxes but offers a rich, in-depth exploration of the entire spectrum of these topics.

How do you calculate the density of related terms?

The formula for calculating the density of a related term is quite straightforward: 

Density = (Number of times the term appears / Total number of words in the content) × 100 

To get the overall RED score, simply add up the densities of all related terms. 

For example, if the density of ‘SEO’ is 2%, ‘Content Marketing’ is 1.5%, and ‘PPC’ is 1%, your RED score would be 4.5%.

This calculation gives you a percentage that represents how frequently the term appears in your content, helping you gauge its prominence.

Interpreting these results is key to understanding the impact of your terms. A higher density means the term is a significant part of your content, which can be good for SEO. However, it’s crucial to avoid overuse, as this can lead to keyword stuffing. Aim for a balanced density that naturally integrates these terms without overwhelming the content.  

What is the optimal RED percentage for your content?

When it comes to RED, finding the sweet spot in terms of percentage is crucial. So, what is the ideal range?

Best RED Percentage: Above 4% and Below 7%

The optimal RED percentage typically falls between 4% and 7%. This range ensures that your content is rich in relevant terms without appearing spammy or over-optimized. Staying within this range can significantly enhance your content’s SEO performance while maintaining readability and quality.

What are the best practices for optimizing RED in your content?

  • Relevance Over Density: Instead of aiming for a specific percentage, focus on including related terms that naturally fit within the context of your content.
  • User Intent: Consider what users are looking for when they search for your primary topic and include related entities that address those needs or questions.
  • Content Depth: A well-researched and comprehensive article that covers various aspects of a topic is likely to naturally have a higher RED.
  • Natural Language: Write in a way that naturally incorporates related entities without forcing them into the content, which can lead to over-optimization.
  • Avoid Over-Optimization: Including too many related terms or entities can make content appear spammy or over-optimized, which can negatively impact SEO.


Always prioritize the reader’s experience. Your content should be informative and enjoyable to read, with RED serving as an enhancement rather than the sole focus.

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