What PageRank (PR) Is

Google’s measure of the number & quality of inbound links to a web site. The PageRank (PR) of each page is one of the about 100 criteria Google uses to rank web pages.

How Much PageRank Matters

It is only one of 100 criteria Google uses, but from experience I’m convinced that it weighs quite heavily in Google’s ranking algorithm. Pages with a high PR value usually outrank pages with a low PR value.

Some search engine experts feel that webmasters in general assign too much value to PR – and they are probably right. A high PR is only valuable if the page is properly optimized for the keywords it targets. The Google homepage has a perfect PR of 10, but it does not rank first for every keyword search.

How PageRank is calculated

Google measures the number and quality of links to a page – both links from outside the site and links from other pages in the same site.
The PR formula is:
PR(A) = (1-d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))

Don’t be discouraged. It’s not as difficult as it looks.

Before I explain how it works, I should mention that this is the original formula used by Larry Page and Sergey Brin when they developed the PageRank system. It is likely that the formula has been tweaked since then.

A = The page for which we want to calculate PR
t1 to tn = All the pages linking to page A
C = The number of outbound links each page has
d = A damping factor (set to 0.85)

Page A has inbound links from pages X, Y and Z.
Pages X and Y each have only one outbound link:
The one to page A. But page Z has three outbound links of which only one points to page A. Page X has a PR of 1, page Y has a PR 2 and page Z has a PR 3.

Here’s this example’s formula:

PR(A) = (0.15) + 0.85(1/1) + 0.85(2/1) + 0.85(3/3)

PR(A) = 0.15 + 0.85 + 1.7 + 0.85

PR(A) = 3.55

So page A has a PR of 3.55.

So page A has a PR of 3.55.
Black shows page A, red shows page X, green shows page Y and purple
shows page Z.
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