The standard width of your blog in Blogger is 660 px. You can change it to a maximum of 1000 px if you're using Blogger Template Designer.
1. Go to your Blogger Dashboard and click 'Design'
2. Click 'Template Designer'
3. Click 'Adjust Width'
4. Change 'Entire Blog' to 1000 px
5. Change both side bars to your desired width (I changed both to 230 px for my blog)
6. Click 'APPLY TO BLOG' before you exit the page
If you don't use a blogger template, please check out the articles below to find our how to edit html to modify the width of your blog.
Related articles on the web:
✎ How to Change Blog Width in Blogger
✎ How to Change Blogger Blog Width
✎ Change the Width of Your Blog - Make the Blog Wider