Forum Moderators: buckworks
And so if you have a PR10 with no other links point to you, you will go up to PR5 ... and possibly to PR8 or even PR9 (this won't happen, so stop dreaming ...). But it might take 1000 PR1 pages which have hundreds of other links on the page to bump your rating.
you can't calculate PR. there's a basic published formula but there are unknowns, most notably the how the actual PR is translated (through some logarithmic function) into the 0 to 10 scale you see in the google toolbar.
if you mean how do you see the PR that google calculated, download the toolbar.