Domain Rating (DR)
a metric and method for calculating the relative value of backlinks to a website (a domain) developed by Ahrefs
Developed by SEO backlink analysis company Ahrefs, the Domain Rating (DR) metric is one of several metrics developed by third parties to help web developers predict how their websites might perform in the The Index, which became more difficult to do when Google disabled outside access to their PageRank metric.
The Ahrefs Domain Rating metric is an unpublished formula, described by the company as starting with a count of how many unique domains have at
least one "dofollow" backlink to the website in question, weighted by the DR values of those linking domains, and by how many unique domains those sites link to.
Obviously this would be a blob of statistical jello, ever quivering, so Ahrefs also applies what they described at one point on their web site as "math and coding magic" presumably to allow the score for a given site to converge on some stable value rather than soak up all the CPU in the universe performing that recursive calculation on an ever-shifting gas cloud of backlink data.
Finally, they normalize the results and plot the scores on a scale from 0 to 100. (Aherfs point out that as the Internet grows, the space inside this arbitrary scale grows.)