I've got 4 Real Estate sites with internal pages PR1-3. If I want to exchage links with a PR4 page, how many links PR1-3 should I put in return?
I agree with the post above... A PR2 site that only links to your site could be worth more than a PR4 site that links to 100.
Assuming the same number of outbound links on each page, the answer is roughly 36. As a general rule, PR seems to be based on a factor of 6. There is certainly no hard evidence on that, but a search of these forums will show that most people think it's in that area. If that's true, then: 6 PR2 = 1 PR3 6 PR3 = 1 PR4 Therefore 36 PR2 = 1 PR4 There are certainly a lot of other factors in play (the biggest being the number of total links on the page), but that should give you a rough idea.
I'm not sure how some people come up with a certain figure. That's just a rough estimation cause the PR algo is much more complex than that.
6 PR2 = 1 PR3 6 PR3 = 1 PR4 Therefore 36 PR2 = 1 PR4 your scenario would bring some kind of PR boost.
PR is divided between the number of links on the page. A page with one link passes 10X the PR as the same page with 10 links. Toolbar PR is also rounded, so a PR 4.01 or 4.99 is going to show as a PR4, yet the 4.99 has approximately 6x the PR juice as the 4.01 - So there is absolutely no way to give an exact number, even IF you didn't have to factor in the links that google doesn't allow to pass PR. Forget about PR and focus on quality links from authority/related sites.