Backlink Gap Calculator: How Many Backlinks Do You Need?

What a backlink gap is

A backlink gap is the difference between the number of sites linking to your page and the number linking to the pages that already rank for the keyword you want. It turns "how many backlinks do I need?" into a number you can plan around.

The calculator counts referring domains, not backlinks. Ahrefs defines a referring domain as a site that the target has one or more backlinks from, so 50 links from one blog are 50 backlinks but 1 referring domain. Counting sites instead of links stops one sitewide footer link from looking like hundreds of separate votes.

It also works at the page level. Google describes its link analysis systems as understanding how pages link to each other, and the page that ranks for a query is what you compete with, not the whole domain behind it. The site's overall strength still matters, which is why the calculator also asks for Domain Rating.

Where to get the numbers for free

You need two sets of numbers, and both should come from the same tool.

• The ranking pages. Paste each result's full URL, not just its domain, into Ahrefs' free Backlink Checker. It shows referring domains, backlinks and Domain Rating (DR) for any website or URL. Compare the referring domains of the ranking pages: a home page with thousands of links tells you little about what a blog post on the same site needs.
• Your page. Check it in the same tool. Google Search Console's Links report also shows your top linked pages and the sites linking to each one. Google says the report shows a sample of links, not every link, so use it as a cross-check rather than an exact count.

Backlink tools build their own indexes (Ahrefs, for example, uses its own crawler, AhrefsBot), so the same page can show different numbers in different tools. Mixing sources skews the gap. The full walkthrough is in how to check backlinks.

How to read your results

• Median is the middle value of the ranking pages you entered. It is the working target, because one page with an unusually large link profile cannot drag it up the way it would drag up an average.
• 75th percentile is the value that roughly three quarters of the ranking pages are at or below. It is the safer target. The calculator switches to it when your site's DR is 10 or more points below the ranking sites' median, because a weaker site usually needs more links to the page itself.
• Outliers are pages with at least five times the median's referring domains (and at least 50 more). They are flagged and left out of the 75th percentile, so one giant page cannot set your safer target.
• Gap is the target minus your page's referring domains. A negative gap means you are already ahead, and links are probably not what holds the page back: check search intent, content depth and indexing first.
• Time at your pace divides the gap by the new referring domains you expect to earn each month, rounded up to whole months.
• Competition level uses the same ranges as our guide to how many backlinks you need to rank: a median of up to 10 referring domains is low, 11 to 40 is medium, and more than 40 is high.

Common mistakes

• Comparing domains instead of pages. A ranking blog post on a big site may have only a handful of links of its own. Look up the exact URL that ranks.
• Counting backlinks instead of referring domains. Sitewide links from one site can add up to thousands of backlinks and still be a single referring domain.
• Mixing tools or scores. DR comes from Ahrefs and Domain Authority (DA) comes from Moz. They are calculated differently, so pick one and use it for every site, including yours.
• Treating every result the same. Skip ads. A forum thread in the top results is often a sign of weak competition, and a big-brand home page ranks on the strength of its whole site. The median keeps one page like that from skewing your target.
• Chasing the number with any link. Links from unrelated sites can fill the gap on paper and still not move rankings. Buying links for ranking purposes is link spam under Google's spam policies.

How to close the gap

Start with the links that cost least and work outward.

1. Internal links. Link to the page from your most visited pages with anchor text that describes it. It is free, and Google finds new pages by following links from pages it already knows.
2. Sites that link to your competitors. Run each ranking page through a backlink checker and list the sites that link to two or more of them. They already cover the topic, so they are your warmest outreach targets.
3. A reason to link. A free tool, a template or original data on the page gives other sites something to cite.
4. Guest posts and listings in your niche. How to get backlinks for a new website covers the methods that work for a site with no links yet.
5. A steady pace. There is no official safe number of links per month. What matters is that links come from relevant sites for real reasons, and that any paid placement is marked with rel="sponsored" or rel="nofollow", which Google's spam policies accept.

If you would rather hand the work off, our backlinks service places links in relevant content and shows every placement in your dashboard.