At Ahrefs we have a couple of quality metrics calculated according to our own algorithms:Ahrefs URL Rating, Ahrefs Domain Rating and Ahrefs Rank.
Ahrefs URL Rating/Ahrefs Domain Rating measure how important the URL/domain is by verifying the number and quality of its backlinks.
Ahrefs' algorithm, calculates a score between 1-100, with 100 being the highest. A rating of 0-30 means the page/domain is unpopular, 31-70 means that it is average and 71-100 indicates that it is very popular.
Ahrefs Rank (also known as Global Rank) is based on Ahrefs Domain Rating and on chart in the Overview tab of Site Explorer we show position of a site in Top 100 million domains.
The lower this value is, the better position in Top 100M analysed website occupies.
This metric is basically similar to Alexa Rank but uses links to rank websites.