A short overview about PageRank (PR)

What actually PageRank (PR) is?

PageRank (PR) is one of the advanced features included in the Google Toolbar displayed like in the figure bellow with a green thin line which is actually showing the PageRank score of a certain page on a scale from 1 to 10. These numeric values are actually much higher but I will talk about it later as well as I will explain it the basics of how it is calculated.

Usually the higher PageRank value a webpage has, the more important and relevant it is considered by Google. PageRank is also one of the many factors which play an important role in the ranking of the pages on the SERPs.

There are actually many discussions on forums among webmasters and SEO experts regarding the real value of PR and what role does it play in the ranking of a website.

How is PageRank calculated?

First in order to be able to check PageRank value of your individual web pages or of some other webpage, you need to download the Google Toolbar which is available for Microsoft IE as well as for Firefox.

It is presumed that the real PageRank value is calculated on a logarithmic scale, thus PR value 0 is actually 0 to 10, PR value 1 is 100 - 1,000 and so on. It is also considered that the internet itself has its own PageRank value but no one knows exactly how it is calculated taking in consideration that there are new pages appearing and disappearing on a daily basis.

In this article about PageRank we are trying to provide you the most acceptable explanations related to PageRank and how it is supposed to be calculated.

Here is the equation which represents most probably how PageRank value is calculated:

PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))

To make it more clear here is a short explanation of the parameters used:

• T1...Tn - are pages linking to page A
• C - represents the number of outgoing links on pages T1...Tn
• d - is a damping factor usually set between 0 - 1
• PR(T1)/C(T1) - represents the share of a vote (ex. PR5/15 = 0.33)

Sometimes it seems to be impossible to make the calculations considering that the PR of a page depends on the PR of other pages pointing to it but the PR value of the pages on the third level backwards also has to be known.

The basic of the trick which solves this problem is that the calculations are repeated as long as the final value doesn't change much or at all.

As we are not mathematicians we are not going to give you an in depth scientific explanation but are presenting one good example which reflects very well how PageRank value is obtained.

Let's suppose the following scenario:

As you can see “Page A„ is linking to “Page B„ which is considered as an outgoing link from “Page A„ parameter C(A) and “Page B„ also has an outgoing link pointing to “Page A„ which is parameter C(B).

So we already have two values which are in the equation:
C(A) = 1
C(B) = 1
Let's set the damping factor “d„ to 0.85 so:
d = 0.85

As we don't know the pages PageRank value we estimate it to PR0 and here are the formulas:
PR(A) = (1 - d) + d(PR(B)/1) = 0.15 + 0.85 * 0 = 0.15
PR(B) = (1 - d) + d(PR(A)/1) = 0.15 + 0.85 * 0.15 = 0.2775


We are repeating the same calculations with the obtained PR values until the results are not changing:
PR(A) = 0.15 + 0.85 * 0.2775 = 0.385875
PR(B) = 0.15 + 0.85 * 0.385875 = 0.47799375

Again:
PR(A) = 0.15 + 0.85 * 0.47799375 = 0.5562946875
PR(B) = 0.15 + 0.85 * 0.5562946875 = 0.622850484375


This was just an example to let you experiment more scenarios with more pages involved with different PR values and outgoing links.