Ipagerank.org lets you check ranking of any website instantly and easily.

How is page rank calculated?

The way in which Google calculates the page rank is based upon links between pages.

Each link from one page to another represents a vote to the page the link points to.

Basicaly, the more links page receives, the higher its importance becomes.

Google updates the pagerank visible in the Google toolbar from time to time (we believe about every three months). The PR displayed is not the current page rank of the URL, but the one from the last toolbar pagerank export.

References:

• Google Technology
• Pagerank Wiki