How to change the sidebar width of Divi
In the Divi theme by Elegant Themes, the sidebar has is 20.875% and the content left area has 79.125% width by default.
It's possible to change the width of the right sidebar with the following CSS code:
#left-area{width: 66.67%;}
#sidebar{width: 33.33%;}
.et_right_sidebar #main-content .container::before {
right: 33.33% !important;
}You can change the numbers as you with. Please add the code in Divi > Theme Options > General > Custom CSS.
Or, you can create a child theme and place the code to the stylesheet file (style.css) under the child theme.
Personally, I love Divi because it's a very simple and fast theme for WordPress. This blog has been built with Divi. (Enfold, which was used before current theme, was also a light-weight theme, whose performance was satisfactory.)
Elegant Themes also runs a blog which provides users with useful tips and tricks on Divi and WordPress.