Most sites, have a nifty little file called 'sitemap.xml` - you can always find it on the top- level :
for example: https://www.apple.com/sitemap.xml or http://visualsitemaps.com/sitemap.xml
With that file ( which is just a bunch of links that tell Search Engines what to index ).. you can count them all to get an idea of scope.
We don't recommend you manually count them of course.. let the browser do that for you!
Step 1: Open Google's Chrome Browser
Step 2: Open the Sitemap.xml url in your browser
Step 3: Command +F (mac) or Cntrl+F (pc) to bring up Search in page.
Step 4: enter 'http:' and voila.. wait for the nodes to be counted!