How to Increase Blogger Width in a Blogger Blog

Step 1: Go to Dashboard- Blog- Design- Edit Html section:

When you sign in to Blogger you are taken to your Dashborad (a list of all your blogs and the blogs you are following). From Dashboard, choose the particular blog you want to format (increase width) and then go to Design of that Blog. Now go to Edit HTML tab inside the Design tab. The Edit HTML tab opens the template editor for you.

Step 2 : Back up  Blog Template:

       Ensure you back up your old template in case you decide to use it again. To do this, click on the "download full template" link and save the file to your hard drive.  

Step 2 : Search for the code :

Use Ctrl+ F and search for, or any portion of the codes below:
 

1000px'

This 1000px is the overall width of the Blogger Blog.
 

Step 4: Change the value 1000px to 1250px:

Now change 1000px to 1250px, I have experimented with 1300 and 1500px but it makes the Blog even wider than the window. So I will not advise them. but 1250px seems to me as the perfect value.