A link gap analysis tells you roughly how many links you need to build to compete for a given keyword. Here is how to do it properly.
The key principle — compare to sites with a similar DR to yours
The most important thing when calculating your link gap is to find sites of a similar authority to yours that are already ranking in the top 10. Comparing yourself to a DR 80 site when your own site is DR 20 will give you a misleading number. Find the sites closest to your own DR that are currently ranking — those are your real benchmarks.
The process:
Use Ahrefs or Semrush to look at your target keyword and find sites of a similar DR to yours ranking in the top 10
Look at their backlink profiles — but filter for dofollow links only with a minimum DR of 20
Don't be misled by the total number of referring domains. What matters is how many of those links carry real weight.
Estimate how many solid, quality links it would take to match or exceed those pages at the page level
With a bit of practice you can eyeball this quickly. A page with a large number of referring domains often has far fewer links with any real authority behind them — meaning the bar is lower than it first appears.
What this tells you...
Once you know roughly how many links you need per keyword, you can estimate the cost to compete for each opportunity and prioritise accordingly. The goal is to build a shortlist of commercially relevant keywords where the link gap is realistic for your budget — and work through them systematically.