There are lots of Tools to Create Sitemap of a blog or website on the internet to submit your sitemap to Google using Google Webmaster tool. But mostly, none of the tool there will be of use to you if you are using Blogger Blogspot as your blogging platform.

Why? This is because blogger automatically creates sitemap for every Blogger Blog. As mentioned by Google Webmaster Help Center, Blogger even submits Sitemap for you.

So, basically if you run a Blogger blog you don’t have to do anything.
However, if you still want to submit your blog sitemap to any other 3rd party service, here is the default the way that you can use,

http://www.blogname.blogspot.com/rss.xml
or
http://www.blogname.blogspot.com/atom.xml

By default, atom.xml only contains 25 posts. If you want you increase the number of posts in your atom.xml, change your URL to:
atom.xml?redirect=false&start-index=1&max-results=100
atom.xml?redirect=false&start-index=101&max-results=100
atom.xml?redirect=false&start-index=201&max-results=100
and so on.
For some reasons, most sites will not have all of their pages indexed, sometimes it may takes times. To improve how Google crawls and indexes your site, you can refer here for more information on Google Webmaster guidelines.