In our Site Explorer tool under the ‘Backlink profile’ tab, you might have seen the URL rating distribution graph on the bottom right hand side of the page. 

In the graph above, the given URL in Site Explorer has 2,014,587 (or 71%) of total backlinks coming from websites with UR 0-10, 811,955 (or 28%) from websites with UR 10-20 and etc.

This shows you the number and percentage of backlinks coming from pages in a given UR (URL Rating) range. UR is measured on a logarithmic scale from 1 to 100, with the latter being the strongest. 

Therefore with regards to UR, the closer to 100, the better. Links from a high authority site will be more powerful than a link from a low authority one.