The RSS subscriber count gives you an idea of the number of unique users who may have subscribed to the RSS feed of a particular website or a blog.
People may subscribe to a RSS feed in different ways – they may use an online RSS reader (like Google Reader or Netvibes), an offline reader (like FeedDemon or Reeder), through email newsletters, toolbars or even mail clients like Microsoft Outlook. The RSS subscriber count is an approximate summation of all these numbers.
Also see: RSS Feed Search Engine
Determining the RSS Numbers
If a site is syndicating its RSS feed via FeedBurner and have made the stats public, you can easily determine the number of RSS subscribers of their feed using the FeedBurner Chicklet.
Just replace XYZ in the above URL with the feed name and you should see an image representing the RSS subscriber count – see example.
However, not all sites may be using FeedBurner and in that case, we can still get an approximate number of RSS feed subscribers using Google Reader.
Go to Google Reader, type the feed address (URL) in the “search by keyword” box and hit Enter. You may also use keywords but a full feed address will show the perfect match.
These numbers are however approximate as they only include the RSS subscriber base of Google Reader, iGoogle and Google Desktop users as determined by Google FeedFetcher.