GeneratePress, a lightweight WordPress theme, is highly customizable. It's possible to set the width of the sidebar in GeneratePress. You can also set the sidebar width in a fixed size (e.g. 350px.)
How to set the width of the sidebar in GeneratePress
If you are using a free version of Generate and you want to specify the sidebar width to 25%, you can use the following code snippet:
// How to set the width of Content and Sidebar areas in free version of GeneratePress
add_filter( 'generate_right_sidebar_width','lh_right_sidebar_width' );
function lh_right_sidebar_width() {
return '25';
}
Add this code to the function file (functions.php) of the theme. Of course, I suggest you to use a child theme.
If you own a premium version, you can easily set the width of the sidebar in Customize > Layout > Sidebars under the WordPress Admin:
If you want to set the sidebar width to 340px, you can use the following CSS code snippet:
/* Set the width of the right sidebar in GeneratePress to 340px */
@media (min-width: 769px) {
#right-sidebar {
width: 340px;
}
#primary {
width: calc(100% - 340px);
}
}
You can change the width as you wish. In this WordPress blog, the width is set to 340px.
How to make the sidebar sticky in GeneratePress
If you want a sticky sidebar, you can just use the following CSS code:
// Make the GeneratePress sidebar sticky
@media (min-width: 769px) {
#right-sidebar {
position: -webkit-sticky;
position: sticky;
top: 0;
}
}
Conclusion
You can easily customize even with a free version of GeneratePress. GeneratePress is a lightweight WordPress theme available for free which is responsive and easy to use. This theme is used on this blog. It's a good option for blogs and also for other purposes.