Another useful instrument in Google Webmaster Tools is the Sitemap section in Site configuration>>Sitemaps:
Figure 1 – Google Webmaster Tools “Sitemaps” Section
You can check your submitted XML Sitemaps in this section and identify which pages from them Google has managed to index. You can also tell if Google had trouble accessing the Sitemap by seeing if there is a checkmark in the “Status” field. That being said, why do we even want to do this? If a site is already “crawlable” in Google’s eyes, why do we need to perform this extra step?
Figure 2 — “Submit a Sitemap” Button
Clicking on the above button reveals a field to enter the physical location of the XML Sitemap, which is usually in your website’s root directory, for instance: www.example.com/sitemap.xml.
Keep in mind that the specific numbers reported in the Sitemaps section of Webmaster Tools only apply to the URLs you submitted in your Sitemap(s), not the amount of pages you actually have in the index; there will always be a discrepancy between the “URLs submitted” and “URLs in web index”:
Figure 3 – URLs in Web Index
In fact, it is rare that the number of URLs reported in both sections will be the same. There could be discrepancies because of restrictions on a lot of files in your robots.txt or just duplicate pages that Google has decided not to index.
Just ensure that URLs in your Sitemap are the “canonical” URLs (www or non-www for example). If there are URLs you care about that aren’t in your Sitemap, just add them in and re-submit. Many times, web developers will add multiple pages to a site and forget to update their Sitemaps. This can be problematic if the new pages are not well interlinked on the site. Remember, your site can have the most optimized pages ever created, but all of your hard work will be in vain if Google doesn’t know about them!