The Google PageRank is a numerical assessment of the importance of a web page. It is sort of like saying, “Okay, rate this web page on a scale of 0-10, where 10 is the most important.” Google uses PageRank to determine how to list its search results.

There are actually two types of PageRanks associated with Google:

  • PageRank: Value ranges from 0-1
  • Toolbar PageRank: Value ranges from 0-10


PageRank


PageRank is a probability equation that basically asks, “If I were to randomly click on a link, what is the likelihood that out of all the pages on the web, I will be directed to page such-and-such?” For example, a page with rank 0.2 means there is a 20% likelihood that clicking on any random link on the web will take a surfer to that page (0.2*100% = 20%). Naturally, few websites have probabilities quite that high.

The equation for calculating this probability is kind of complex and I’m not going to delve too far into the math details here (read this article on Wikipedia if you want to step-by-step breakdown of the algorithm). Essentially, what it comes down to is this: Each page on the web has a PageRank, and each page on the web has X number of outgoing links (where clicking on a link will take you to another web page). To find the PageRank for a web page, you take all the web pages on the internet and sum the following: PageRank_for_that_page [divided by] Number_of_outgoing_links.

Let’s me illustrate. If a website with PageRank = 1 (it is the most important site on the internet) has only only one outgoing link (say, to your web page), then your web page will now have a PageRank >= 1 (although 1 is as high as you can go). (Note: This example is not quite accurate because Google takes other factors into account as well, but it demonstrates the general principle). If, however, a website with PageRank = 1 has 1000 outgoing links, and your web page is one such link, then your PageRank will get bumped up by only 1/1000 = 0.001. Quite a difference!

For those of you out there who are mathematically inclined, it might be interesting to note that although the example I gave above assumes a linear PageRank scale, it is likely that the PageRank scale is logarithmic (although no one outside of Google knows for sure). This means that if the scale is log base 10, then it takes 10 times your previous sum to bump up in rank from 0.1 to 0.2 than it did to bump up from 0 to 0.1. That would mean that a website with a high PageRank probably gets multiplied by some additional value, and does not just have its rank divided by the number of its outgoing links, since it’s much harder to achieve a high PageRank than a lower one, so its link “recommendations” are much more valuable than a link recommendation from a page with a lower PageRank.

For those of you not mathematically inclined, there is no real need to worry about the scale — the principle is all that matters. Basically, you want sites with high page ranks to link to your site, and the more sites linking to you, the better.

* PageRank is recalculated each time Google crawls the web.


Toolbar PageRank


Toolbar PageRank is the rank you are shown if you request to see your Google PageRank either through the Google Toolbar or through page rank checkers. It is related to PageRank, but its formula is not exactly based on it (that is, it’s not just a power of ten conversion. A PageRank of 0.2 won’t necessarily give a Toolbar PageRank of 2). Unfortunately, Google has not chosen to make its algorithm known for calculating the Toolbar PageRank. It should only be used as a rough guide anyway, since values are only updated about once a year (so a website that goes from being the least popular to the most popular site on the web would have to wait a year to see its Toolbar Page Rank change from 0 to 10).

Not everything that has a Toolbar PageRank has an actual PageRank. This can happen if the page has not been indexed by Google, but another page on the website has. The Toolbar will then calculate a Toolbar PageRank based on that rank on the fly, even though the page does not actually have a Google PageRank. This is important to realize, because if you link to a page that has not been indexed by Google, it will actually hurt your PageRank. To avoid this, make sure you can find a page on Google, and that there is some sort of description under it. If you cannot, then it hasn’t been indexed.

* Toolbar PageRank for indexed pages is recalculated once per year. The last update was April 3, 2010.


Some Important Conclusions


Your PageRank will increase with:

  • The more pages you have on your website.
  • The more links point to your page from other websites.
  • The more important the other websites pointing to you are.
  • The less links you have pointing to other websites.*

* I didn’t really go into this here, but basically your website has a certain amount of PageRank that it can “spread” to the internal pages on your site (those pages that are under the same domain name, not pages on other websites). This amount increases with the more unique pages you have (Google penalizes websites that have a lot of pages that are identical or mostly the same), and decreases with the number of outgoing links (links to other websites) that your website has. This affects the PageRank of all the pages on your website, not just one. Note: If you have no links pointing to other websites, Google assumes that you are pointing to ALL the websites on the internet. Basically, don’t become a link farm and link to everything, but don’t link to nothing, either. Be discerning in your links, that’s all. After all, if no one linked to anybody, everyone would have PageRanks = 0.