The Google PageRank algorithm is logarithmic and not linear and most SEO’s believe the base is between 8 and 9. The following takes into account a base of 8 in the Google PageRank Algorithm.
There are two types of pagerank.
- Toolbar pagerank with is the little green bar that can be found it the Google Toolbar.
- Real pagerank is what Google uses in their algorithm to determine importance of a page in comparison to other pages on the web.
Both of these are query independent metrics. It is also important to note that this is a page level metric and not a domain level metric. Meaning a website is not a PR 6, but rather a webpage is a PR 6. So a websites home page can be a PR6 yet its internal pages could all be PR 2.
PR 0 = Less than 4 Real PageRank Points
PR 1 = 8 Real PageRank Points
PR 2 = 64 Real PageRank Points
PR 3 = 512 Real PageRank Points
PR 4 = 4096 Real PageRank Points
PR 5 = 32768 Real PageRank Points
PR 6 = 262,144 Real PageRank Points
PR 7 = 2,097,152 Real PageRank Points
PR 8 = 16,777,216 Real PageRank Points
PR 9 = 134,217,728 Real PageRank Points
PR 10 = 1,073,741,824 Real PageRank Points
SEOmoz Video: What is Google’s PageRank Good For?
In the Following video Rand explains what SEO’s and site owners should and should not use Google’s toolbar pagerank for when analyzing sites for value and link opportunities.
What does this all mean to the average SEO trying to figure out why site A is outranking Site B. Not much, since this metric only reports importance of pages on the web and is query independent. This means that a site that technically has less links, less pagerank (importance) could rank higher for specific queries if other signals such as anchor text is more focused on the query term.
It can be used to compare with other metrics such as MozRank to determine if a page has been devalued by Google. For example if a page has a pagerank of 3 but the MozRank is a 6, that gives a pretty good indication that Google found out the site was buying or selling links, and thus dropped its toolbar pagerank.
It can also be used to get a rough estimate of raw link popularity (but don’t let this be a guide because based on what we have seen it’s not always a good indicator).
Finally it is useful to look at the history of a websites pagerank score to get an idea of if and when it was devalued. There is a great tool for finding the historical pagerank of a webpage at SEOmoz.
Additionally if you want to read the original pagerank paper you can head over to Sergey Brin’s and Larry Page’s original paper titled The Anatomy of a Large-Scale Hypertextual Web Search Engine.
We assume page A has pages T1…Tn which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0 and 1. We usually set d to 0.85. There are more details about d in the next section. Also C(A) is defined as the number of links going out of page A.
The PageRank of a page A is given as follows:
PR(A) = (1-d) + d (PR(T1)/C(T1) + … + PR(Tn)/C(Tn))
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