How many keywords should be in a cluster?

A typical cluster contains 5 to 30 related keywords that share the same search intent. The exact number depends on the topic breadth. A narrow topic like 'what is content decay' might have 5 to 10 variations, while a broader topic like 'Instagram marketing strategy' could have 20 to 30 related terms. The key criteria is shared intent, not a specific count.

What tools can you use for keyword clustering?

Semrush's Keyword Strategy Builder, Ahrefs' Keywords Explorer, and SE Ranking all offer clustering features that group keywords by SERP similarity. Free alternatives include manually checking Google search results to see which keywords return the same URLs in the top 10 - if two keywords show overlapping results, they belong in the same cluster.

What is the difference between keyword clustering and topic clusters?

Keyword clustering groups related search terms that should be targeted by a single page. Topic clusters organize multiple pages around a central pillar topic. They work together - keyword clustering helps you decide what goes on each page, while topic cluster strategy determines how those pages link together and build topical authority.

What Is Keyword Clustering for SEO?

Keyword clustering is the practice of grouping related keywords that share the same search intent and targeting them with a single page rather than creating a separate page for each individual keyword. Instead of writing 10 articles for 10 similar search terms, you identify that all 10 terms are looking for the same answer and write one comprehensive page that covers them all.

Why Does Keyword Clustering Matter for SEO?

The old approach to SEO was to create one page per keyword. If you wanted to rank for "content velocity," "publishing frequency SEO," and "how often to publish blog posts," you would create three separate pages. This approach leads to keyword cannibalization - your own pages competing against each other in search results - and thin content that fails to demonstrate expertise.

Modern search engines understand semantic relationships between queries. Google recognizes that "content velocity" and "how often should I publish content" are essentially the same question. The Semrush 2024 Ranking Factors Study analyzed over 300,000 search positions and found that text relevance - how well your content matches search intent - has the highest correlation with rankings at 0.47, nearly 3x higher than any other factor including backlinks.

This means one comprehensive page that thoroughly covers a topic will outrank multiple thin pages targeting individual keyword variations. Ahrefs' SEO research confirms this - the average number-one ranking page also ranks for roughly 1,000 other keywords. These pages rank broadly not because they stuff keywords but because they cover the topic comprehensively enough to match many related queries.

How Do You Build Keyword Clusters?

Step 1: Collect Your Keywords

Start with a seed keyword and expand. Use tools like Semrush, Ahrefs, or Google's own autocomplete and "People Also Ask" features to build a list of related terms. For a topic like "video marketing," your initial list might include:

what is video marketing
video marketing strategy
video marketing for startups
how to use video for marketing
video marketing benefits
video content marketing
video marketing ROI

Step 2: Group by Search Intent

Check the actual search results for each keyword. If two keywords show mostly the same URLs in the top 10 results, they share intent and belong in the same cluster. If the results are completely different, they represent different intents and need separate pages.

There are three common grouping methods:

SERP overlap analysis - The most reliable method. Compare the top 10 results for each keyword pair. If 3 or more URLs appear for both keywords, they belong in the same cluster.

Semantic similarity - Group keywords that describe the same concept using different words. "Video hook" and "scroll-stopping opening" are semantically similar even if the SERPs differ slightly.

Modifier-based grouping - Keywords with common modifiers (what is, how to, best, vs) often indicate different intents. "What is video marketing" (informational) and "best video marketing tools" (commercial) typically need separate pages.

Step 3: Assign One Page Per Cluster

Each cluster gets a single page. Choose the primary keyword (usually the highest-volume term) as your main target, and use the other keywords in the cluster as subheadings, related terms, and natural language throughout the content.

For example, a cluster around "content pillar" might include:

Primary: what is a content pillar
Supporting: content pillar strategy, pillar page SEO, how to create pillar content, content hub strategy

All of these terms get addressed within one page on content pillars rather than five separate thin pages.

How Does Keyword Clustering Fit Into Content Strategy?

Keyword clustering is the tactical foundation for a broader topical authority strategy. Here is how the layers connect:

Keyword clusters determine what goes on each page. They prevent you from creating duplicate or competing content.

Content pillars organize your clusters into a hierarchy. The pillar page covers the broad topic, and cluster pages cover specific subtopics - each informed by its own keyword cluster.

Internal linking connects the pages. Cluster pages link to each other and back to the pillar page, creating a clear topical structure that search engines can follow.

This approach is why we organize our own content at Conbersa into clusters. Our learn pages on content velocity, content decay, and content refresh all link together and reinforce each other's topical signals. Each page targets its own keyword cluster, but together they build authority on the broader topic of content strategy.

Common Keyword Clustering Mistakes

Creating too many clusters. If you have 50 clusters for a single topic area, some of them probably share intent and should be merged. Fewer, more comprehensive pages outperform many thin ones.

Ignoring search intent. Two keywords might look similar but have completely different intents. "Video marketing statistics" and "video marketing strategy" seem related but searchers want different things - one wants data, the other wants a plan. Check the SERPs before grouping.

Clustering once and never revisiting. Search intent shifts over time. Keywords that used to require separate pages might converge, or a single page's cluster might split as the topic becomes more nuanced. Review your clusters quarterly.

Skipping the SERP check. Do not cluster keywords based solely on topical similarity. Always verify by looking at actual search results. The data tells you what Google considers similar - your assumptions are often wrong.

Keyword clustering is not complicated, but it requires discipline. The payoff is a content library where every page has a clear purpose, no pages compete with each other, and the overall site demonstrates comprehensive expertise across your target topics.