Keyword difficulty (KD) is a score from 0 to 100 that an SEO tool assigns to a keyword to estimate how hard it is to rank in the top 10 results. Higher means harder. It is a tool metric, not a value from Google (assessment).
How is keyword difficulty calculated?
Each vendor uses its own formula. Ahrefs looks at the top 10 results and counts the referring domains pointing to those pages. Its scale is not linear: according to Ahrefs (as of October 2026), KD 10 corresponds to about 10 referring domains, KD 40 to about 56, and KD 80 to about 353. Ahrefs states that KD ignores on-page factors.
Semrush describes KD% as an estimate of how hard it is to rank a new page in the top 10. It combines link data of the ranking pages with keyword characteristics such as SERP features, and groups the result into six bands from “very easy” (0 to 14) to “very hard” (85 to 100).
How should you read it?
A 50 in one tool does not match a 50 in another, so compare scores within a single tool. The score also says nothing about your own site’s authority or whether the content fits the search intent. Check the actual results page before deciding.
Example
Invented values for illustration:
| Keyword | KD | Monthly volume |
|---|---|---|
| coffee grinder | 62 | 12,000 |
| burr grinder for french press | 21 | 500 |
Frequently asked questions
What is a good keyword difficulty? Tools label lower scores as easier. What is realistic depends on the strength of your site.
Sources
- Keyword Difficulty - Ahrefsahrefs.com
- Keyword Overview and Keyword Difficulty - Semrushsemrush.com
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