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Google PageRank Algorithm

The Google PageRank of all web pages on the World Wide Web can be calculated by a formula. The Google PageRank Algorithm is that PageRank of web pages can be gained by vote. Remember that a vote is a link back from other web page. The more quality votes a web page have, the higer PageRank that web page will be. Here's the Algorithm or formula of PageRank:

Formula of Google PageRank


PR = short for PageRank

PR[Page A] = PageRank of Page A (e.g. Home Page)

PR[Page 1] = PR value of Page 1 that has a Backlink to Page A

Q[Page 1] = number of Outgoing Links of Page 1

d = damping factor. This should be a value between 0.5 to 0.85. Most people believe that 0.85 is most probably be used by Google. However we think that the damping factor may varies according to the PageRank value the the "voting pages" to reflect the importance and value of the link. For example, d may be 0.5 for web pages with PageRank 1, d may be 0.85 for web pages with PR 10. In other words, d may varies between 0.5 and 0.85 depending on the PageRank values of the "voting pages". For simplicity, all our examples shown in our website will also use 0.85 as the damping factor.

The PageRank value calculated is a Real PageRank value. This can be ranged between 0.15 to billions. This is different from the Toolbar PageRank value that display on Google ToolBar which range between 0 to 10. We have a seperate page for this topic.

From now on, all our examples will use 0.85 for d (damping factor). Therefore the Algorithm or formula will become a bit simpler as below:

Google PageRank Formula with 0.85 damping factor

Take some time to look at the Google PageRank Algorithm again. Isn't the PageRank formula simple enough?

To better understand how the Google PageRank formula works, let's take a simple example here before we plunge into deeper.

Google PageRank Algorithm Introductory Example

Page A has two backlines - a Backlink from Page 1 with PageRank value of 4 and a Backlink from Page 2 with PageRank value of 2. Page 1 has two outbound Links and Page 2 has only one Outbound Link. Please see the diagram below:

Google PageRank Algorithm Example

  • The average PageRank value of all web pages on the World Wild Web is ONE. In other words, the Total PageRank on the World Wild Web is:

    Total PageRank on WWW = Total Number of Pages x 1

    If there are 1,000,000,000 web pages on the WWW, the Total PageRank on WWW is 1,000,000,000

    Therefore when the PageRank value of a page increase, there MUST be some pages losing the PageRank.

  • Incoming Links will increase the PageRank value of a page.

  • Outgoing Links will loss a portion of PageRank to the linked page

When Page 1 place a link to Page A, the PageRank value of Page A has been changed. And the PageRank value of Page 1 will also be changed. If the PageRank value of Page 1 has been changed, then the PageRank value of Page A has to be re-calculated again..........! It seems to form an endless calculation circle!

At first glance, it seems an endless calculation circle. However the strange thing is that every time we run a PageRank calculation of a page, the PageRank value of the Page will be closer to the final value. In other words, if we repeat doing the calculation for a lot of times, the PageRank values of the pages will not be changed much or even stable. Please check the coming examples and everything will be cleared.

This page provides an introductory of Google PageRank Algorithm.

how to improve Google Page Rank