Keyword Difficulty: How to Choose Keywords You Can Actually Rank For

What is keyword difficulty?

Keyword difficulty is a score, usually from 0 to 100, that an SEO tool assigns to a keyword to estimate how hard it would be to reach the first page of Google for it. It is not a Google metric: it is a prediction made by each tool with its own formula, and most of those formulas lean heavily on the backlinks of the pages already ranking.

A bakery owner opens a keyword tool and types “sourdough bread”. The tool shows a difficulty of 72, in red. She switches to “sourdough starter for beginners”: 18, in green. It is tempting to read those numbers as a verdict. They are a starting point. The score knows nothing about her site, her expertise or what the people searching actually want to read.

The short definition lives in our glossary entry on keyword difficulty. This guide goes further: what the score measures, why tools disagree, and how to decide whether a keyword is winnable for your site.

What do keyword difficulty scores actually measure?

They mostly measure the link strength of the pages ranking today. That is the common core; the details differ from tool to tool, and the tools say so themselves.

Ahrefs describes a deliberately simple method: it pulls the top 10 ranking pages for a keyword and looks up how many websites link to each of them. The more links those pages have, the higher the score. Its blog gives a rough scale: at KD 0 to 5 the top pages barely have backlinks, around 50 they have a couple of hundred, at 90 and above they have thousands.

Semrush documents a mix of factors:

Keyword difficulty calculation is based on a variety of factors such as the median number of referring domains pointing to the URLs that are ranking, the median ratio of dofollow/nofollow links pointing to these, the median authority score of the domains that are ranking, and the SERP-related qualities of the keyword itself.

Semrush Knowledge Base, What is KD%?

Semrush then splits the scale into six levels, from 0-14 “very easy” to 85-100 “very hard”, with advice for each one: quality content focused on intent at the low end, quality backlinks from 50 upward, link building plus on-page work and promotion at the top.

Neither page gives the exact weighting of its formula. What both make clear is the main input: links pointing to the ranking pages and to their domains. That matches something Google does confirm. Its ranking systems guide states that it has systems that understand how pages link to each other, PageRank among them, and that PageRank “continues to be part of our core ranking systems”.

But links are only one signal among many. The same guide opens by saying Google’s automated ranking systems “look at many factors and signals” to present the most relevant, useful results. A difficulty score built on links is a reasonable proxy for one part of the competition, not a model of how Google ranks.

Why does the same keyword get a different score in each tool?

Because every tool computes it differently, with different data. Ahrefs says it plainly in its own article:

These tools all use the same 0-100 scale, but each one calculates it differently. If you check the Keyword Difficulty of the same keywords in different SEO tools, the numbers will vary quite substantially.

Ahrefs Blog, Keyword Difficulty: How to Estimate Your Chances to Rank

Three things explain the gaps:

Source of the gap	What changes
The formula	One tool counts linking websites to the top 10 pages; another blends referring domains, link types, domain authority and SERP qualities
The data	Each tool crawls the web with its own index of backlinks, so the link counts themselves differ
The snapshot	Results change with location, language, device and time; a score reflects the results the tool saw when it last checked

That third point comes from Google. Its guide to how Search works explains that relevancy can depend on “the user’s location, language, and device”, and gives the example of a query for bicycle repair shops showing different results in Paris and in Hong Kong. A score computed on one country’s results says little about another.

The practical consequence: never compare a score from one tool with a score from another, and do not treat 40 as twice as hard as 20. Pick one tool, stay with it, and compare keywords against each other inside it.

What does the score not tell you?

It does not know your site. Ahrefs makes the point itself: its score tells you how hard it is for the average website to rank, but “it doesn’t account for your specific website’s authority”. A KD of 45 means one thing for a ten-year-old site with hundreds of linking domains and something very different for a site launched last month.

The score also leaves out most of what you see when you actually open the results page:

• Intent. Do the top results answer the question you plan to answer, in the format you plan to use?
• Content quality. Are the ranking pages accurate, current, written by someone who knows the topic? Or thin, outdated, generic?
• Weak spots. Is there a forum thread, a small blog or a page with almost no links in the top 10?
• SERP features. Does the page show a map pack, images, videos, a shopping block or other features that push the organic results down?

Google confirms that the shape of the page depends on the query: in the same guide, a search for bicycle repair shops “will likely show local results and no image results”, while “modern bicycle” is more likely to show images. A low difficulty score on a query dominated by a local pack is less attractive than it looks if you are not a local business.

How do you judge if a keyword is winnable for your site?

Run four checks, in this order: your authority versus the score, the intent, the quality of the top 10, and the features on the page. The score opens the analysis; the results page closes it.

1. Your authority versus the score. The most useful benchmark, suggested by Ahrefs, is to look up the difficulty of the keywords your site already ranks for, in the same tool. If your pages sit on page one for keywords around 20, a keyword at 25 is realistic, and one at 70 is a long project. If you have no rankings yet, start at the bottom of the scale.

2. The intent. Search the keyword and read the first ten results. Are they guides, product pages, tools, comparisons, local listings? If they are all free tools and you plan to write an article, the score does not matter: you are offering the wrong format. Ahrefs tells this story about its own backlink checker page, which only climbed once the landing page became a free tool, like the pages ranking around it.

3. The quality of the top 10. Open the pages. Look for outdated information, missing expertise, vague answers, pages that rank on brand strength alone. Every weakness you find is a reason to target a keyword despite a middling score.

4. The SERP features. Note what sits above and between the blue links. If most of the screen goes to ads, a map or a carousel, even a first position brings fewer visits than the volume promises.

Before trusting a score, answer these questions honestly:

Is this keyword winnable for your site?7 questions

1. Does your site already rank on page one for keywords with a similar difficulty, in the same tool?

   YesNoNot sure

2. Do the top results use the same format you plan to publish (guide, product page, tool, comparison)?

   YesNoNot sure

3. Did you open the top 10 pages and find at least one weak, outdated or off-target result?

   YesNoNot sure

4. Are there pages with few links or small sites among the top results?

   YesNoNot sure

5. Do organic results stay visible near the top of the page, without being buried under maps, ads or carousels?

   YesNoNot sure

6. Can you bring something the ranking pages lack (experience, data, examples from your business)?

   YesNoNot sure

7. Is the keyword relevant to what you sell or do?

   YesNoNot sure

See my result

A practical method to shortlist keywords

The goal is not a list of easy keywords: it is a short list of keywords that are relevant to your business, realistic for your site, and worth the effort.

1. Start from topics, not scores. Write down the problems your customers bring you, in their words. A free keyword generator turns each topic into variations sorted by intent: questions, comparisons, buying terms.
2. Add volume and difficulty from one tool. Keep the same tool for every keyword so the numbers are comparable.
3. Remove what does not fit your business. A keyword can be easy and popular and still bring visitors who will never buy from you.
4. Set your threshold from your own rankings. Mark the keywords near the difficulty of those you already rank for. Put the rest aside, do not delete them.
5. Read the results page for each survivor. Intent, quality of the top 10, weak spots, SERP features: the four checks above.
6. Group by topic. Keywords that share an intent belong to the same page. Related questions become articles linked to a main page.
7. Order the plan. Start with the most relevant, most winnable topics, and plan the harder ones as later steps.

When should you target a hard keyword anyway?

When the keyword is central to your business, and you are ready to treat it as a long-term project rather than a single article.

Ahrefs, which builds one of the best-known difficulty scores, explicitly encourages it: for many of the KD 70+ keywords it ranks for, it says it took “four to five rewrites, lots of promotion, and many years of patience”. The lesson is not that difficulty is meaningless. It is that a hard keyword is a commitment, not a lottery ticket.

A hard keyword is worth it when:

• It describes what you sell. The main term of your offer, the one your best customers type. Being absent from it has a cost.
• The top 10 has visible gaps. Outdated content, wrong format, generic pages ranking on brand alone. Ahrefs calls these “cracks” in the results.
• You can build toward it. Start with the specific, easier questions around the topic, link those articles to a main page, and let that cluster strengthen the page that targets the broad term.
• You have something to add. First-hand experience, original data, real examples. Google’s ranking systems guide describes its helpful content system as designed to show “original, helpful content written by people, for people”.

It is not worth it when the keyword is only loosely related to your business, when the results all come from a type of site you are not (marketplaces, government pages, major media), or when you have no time to update and promote the page over months.

The bottom line

Keyword difficulty is a useful filter and a poor verdict. Use it to compare keywords inside one tool, read it against your own authority, and always open the results page before deciding. The best keywords for a small site are rarely the easiest ones: they are the relevant ones where the current results leave room for a better answer.

Once your keywords are chosen, the next question is how to write the pages without cutting corners: the guide on AI content and Google covers what Google’s rules allow. And if your audience also asks AI assistants, GEO: get cited by ChatGPT, Gemini and Grok explains how those answers pick their sources.