Formula Google Uses to Calculate the Pagerank

Formula Google Uses to Calculate the Pagerank

Google has developed a technology to determine the quality of a website called the Pagerank or PR. The Pagerank is a number between 1 and 10, with 10 being the best. As a website owner you strive for the highest possible Pagerank. In this article i will show you the formula that Google uses to calculate the Pagerank of a website or individual page.



Pagerank calculation

Google keeps the formula for determining the Pagerank a secret. Otherwise people could abuse it. The formula has changed over the years. Still, some things that determine the PR are public. Google looks at the incoming and outgoing links from your website.

Sites with a high Pagerank linking to your site are worth more than sites with a lower PR. And hundreds of links from sites with Pagerank 2 are perhaps less valuable than one inbound link from a site with Pagerank 5. The scale of Pagerank is logarithmic, meaning that for example 10 links can get you a PR 1, but for a PR 2 you need 10x10 = 100 links to your site.

Formula to calculate Pagerank

There is a small part of the famous formula that Google uses to calculate the Pagerank public. This formula is not complete and it is not known how far this formula is up to date.

Example of the formula:

PR (A) = (1 - d) + d * SUM ((PR (I-> A) / C (I))

Explanation of terms:

• PR (A) is the Pagerank of your web page A.
• d is the damping factor and is typically 0.85. For example, if a page with a PR of 10 with only one link to another web page, than this page gets  a value of 8.5. In this way, a linked page ranks lower than its referrer. The PR is then if it were muted.
• PR (I-> A) is the Pagerank of page I pointing to your site.
• C (I) is the number of links from I that refer to other sites.
• PR (I-> A) / C (I) is the value that your page A gets from page I passed through in the Pagerank calculation.
• SUM (PR (I-> A) / C (I)) Finally, the sum of all values of data pages that link to your page A.

The Pagerank formula explained in words

The Pagerank of your pages is determined by the PR of each page that points to your page A. The PR of referring page's is divided by the number of outgoing links, and those results are added together and multiplied by 0.85.

Finally, 0.15 is added to the Pagerank to determine your page A. Google repeats this formula a few times to create a individual PR for all indexed pages.