The Google PageRank (PR) is calculated for every webpage that exists in Google's database. It's real value varies from 0,15 to infinite, but for representation purposes it is converted to a value between 0 and 10 (from low to high). The calculation of the PR for a page is based on the quantity and quality of webpages that contain links to that page.
According to Sergey Brin and Lawrence (Larry) Page, Co-founders of Google, the PR of a webpage is calculated using this formula:
PR(A) = (1 - d) + d * SUM ((PR(I->A)/C(I))
Where:
PR(A) is the PageRank of your page A.
d is the damping factor, usually set to 0,85.
PR(I->A) is the PageRank of page I containing a link to page A.
C(I) is the number of links off page I.
PR(I->A)/C(I) is a PR-value page A receives from page I.
SUM (PR(I->A)/C(I)) is the sum of all PR-values page A receives from pages with links to page A..
