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I am not sure when this happened, but fairly recently, Google has changed the number of Sitemaps you can reference in a Sitemap index file. The number use to be 1,000 sitemaps can be referenced in a Sitemap index file, now the number is 50,000 Sitemaps. This is a huge increase in capacity.
Still, each Sitemap file can contain up to 50,000 URLs, so technically 50,000 multiplied by 50,000 is 2,500,000,000 or 2.5 billion URLs can be submitted to Google via Sitemaps. That is if I can add correctly.
Googler, Jonathan Simon, said this in a Google Webmaster Help thread:
Thanks for resurfacing this thread as we've improved our capacity a bit since then. The limit used to be 1,000.The Help Center article you point to is correct. The current maximum number of Sitemaps that can be referenced in a Sitemap Index file is 50,000.
Forum discussion at Google Webmaster Help.
Comments:
Oge Nwaozuzu
03/26/2012 09:22 am
Hi Barry - does this also apply to RSS Feeds? What is the limit for the no of entries in an RSS feed?
angelxmoreno
05/29/2014 09:11 pm
According to https://support.google.com/webmasters/answer/71453?hl=en "You can submit up to 500 Sitemap index files for each site in your account." and according to https://support.google.com/webmasters/answer/183668?hl=en&ref_topic=4581190 "A Sitemap file can contain no more than 50,000 URLs and must be no larger than 50MB when uncompressed" so that means the total urls than can be submitted is 500 X 50K = 25,000,000 ( 25 million urls)