How to Check Keyword Difficulty (and Why Every Tool Disagrees)

The biggest mistake I see is treating a difficulty score as a universal truth. Ahrefs says it plainly in its own guide: almost every keyword tool has a difficulty score, they all use the same 0 to 100 scale, and each one calculates it differently. A keyword can be 'easy' in one tool and 'hard' in another on the same day.

Step by step: check keyword difficulty for free

1. Open a free difficulty checker, such as Ahrefs' Keyword Difficulty Checker, or a free account in a keyword tool you already use.
2. Enter the keyword and choose the country you want to rank in. Difficulty is per market.
3. Read the score and the band label next to it.
4. Look at the list of pages ranking now: how many sites link to each, and are they big brands or sites like yours?
5. Search the keyword yourself and note the SERP features, ads and AI Overview above the organic results.
6. Decide: target it now, target it later once you have more links, or pick a narrower version.

How the main tools calculate it

Tool	What the score is built on	Scale
Ahrefs (KD)	The number of referring domains pointing to the top 10 ranking pages	0 to 100, not linear
Semrush (KD%)	Median referring domains, median dofollow and nofollow ratio and median authority score of ranking domains, plus SERP qualities	0 to 100%, in six bands
Moz (Difficulty)	Moz's own Difficulty metric in Keyword Explorer, shown alongside Organic CTR and Priority	Moz's own scale

Ahrefs adds a detail most people miss: its score estimates the chance of getting into the top 10, not the top 3 or number one, and it describes its KD as an absolute metric based on the backlink profiles of the top-ranking pages, not one that's relative to your site.

Turning a KD score into a link target (Ahrefs)

This is the most useful single table in keyword research, because it turns an abstract number into something you can plan for. Ahrefs publishes the approximate number of referring domains a page needs to reach the first page at each KD level:

Ahrefs KD	Referring domains needed (approx.)
0	0
10	10
20	22
30	36
40	56
50	84
60	129
70	202
80	353
90	756

Notice how the curve bends. Going from KD 10 to KD 20 roughly doubles the links needed, but going from KD 80 to KD 90 more than doubles a number that's already in the hundreds. That's why the top end of the scale is out of reach for most small sites, whatever the content.

Read it with your own numbers. If your best pages have links from a dozen sites, a KD 40 keyword that wants around 56 is a long-term goal, while KD 10 to 20 is realistic now.

Semrush's six difficulty bands

KD%	Semrush label	What Semrush says it takes
0 to 14	Very easy	The best starting point for new pages
15 to 29	Easy	Quality content focused on the keyword's intent
30 to 49	Possible	Well-structured, optimised content
50 to 69	Difficult	Quality backlinks plus well-optimised content
70 to 84	Hard	A lot of effort on backlinks and unique content
85 to 100	Very hard	Heavy link building, on-page SEO and promotion

Keyword difficulty is not 'competition' in Keyword Planner

Ahrefs makes a point worth repeating. Google Keyword Planner has a 'Competition' column, and people confuse it with difficulty. Competition only refers to paid search: how many advertisers bid on a keyword. Keyword difficulty is about organic results. A keyword can have high ad competition and low organic difficulty, or the other way round.

What the score can't see

• Search intent. If Google shows product pages and you're writing a blog post, the score doesn't matter: you're the wrong page type.
• SERP features. A low-difficulty keyword under an AI Overview, a map and a video block may send very few clicks.
• Your topical strength. A site with lots of good pages on a subject often outranks the score's prediction.
• Content quality. Links are the input to most scores, but a page that answers better can win against stronger links on smaller searches.

Worth a look next: my guide to finding a keyword's search volume.

How to pick keywords using difficulty

For a small or new site, start with keywords in the easy bands that match what you sell or know, with clear intent and a results page that isn't swamped with features. Build a cluster of those, link them together, and come back for the harder head terms once you've earned links. If you're choosing a tool for this, my comparisons of Mangools alternatives and Keywords Everywhere alternatives cover the budget options, and Semrush alternatives covers the full suites.

My verdict

Use one tool's difficulty score consistently, so you're comparing like with like, and always open the results page before you commit. The Ahrefs referring-domains table is the best reality check there is: if you can't see where the links would come from, pick an easier keyword and win that first.

Another number worth knowing is explained in my guide to checking page authority for free.

Frequently asked questions

How do I check keyword difficulty for free?

Use a free checker such as Ahrefs' Keyword Difficulty Checker or a free tier of a keyword tool, enter the keyword and your country, and read the 0 to 100 score.

What is a good keyword difficulty score?

For a new or small site, Semrush calls 0 to 14 very easy and 15 to 29 easy. On Ahrefs, lower scores need fewer referring domains to reach the top 10.

Why do Ahrefs and Semrush show different difficulty?

Ahrefs says every tool uses the same 0 to 100 scale but calculates it differently. Ahrefs uses referring domains to the top 10; Semrush blends several link and SERP factors.

Is keyword difficulty the same as competition in Keyword Planner?

No. Ahrefs notes that Keyword Planner's Competition refers only to paid search, while keyword difficulty applies to organic results.

How many backlinks do I need to rank?

Ahrefs' table suggests about 56 referring domains for a KD 40 keyword and about 129 for KD 60 to reach the top 10. Treat these as rough guides.