How these scores are calculated
Each tool crawls the web with its own bot and builds its own link index. Ahrefs documents its method: Domain Rating shows the strength of a site's backlink profile compared with the other sites in its database. A domain's rating is passed on to the domains it links to, split equally among them, so a highly rated site that links to only a few others passes more than one that links to thousands. The result is scaled to a 0 to 100 range.
Moz and Semrush use their own models, so the three scores for the same site often differ by several points.
What the score does not tell you
These metrics are commercial estimates, not Google data. Ahrefs itself says Domain Rating correlates with rankings, but less well than its page-level metric, URL Rating. A high score guarantees no position and can be inflated with low-quality links, which makes it a risky criterion for hiring an SEO vendor or buying a website.
Using it well
- Compare: benchmark against the sites on page one for your target queries, not an abstract average.
- Vet partners: combine the score with topical relevance and real traffic before asking for a link.
- Track a trend: a curve that rises over a year reflects steady link acquisition.
- Go page level: for a given query, the link strength of the ranking page matters more than the domain's.
What to aim for instead
The metrics that matter are the number of relevant referring domains, rankings for your money keywords, organic traffic measured in Search Console and the leads it produces. A local business can dominate its city with a modest score simply because its direct competitors score no higher, which is why chasing a number for its own sake rarely pays off.