How do I change post page width?

Hi everyone,

Is it possible to modify the width of a post on the post page? I’d like to keep the post page & the main page sizes the same. I noticed that on an individual post the width is smaller.

I’m not sure if this is a feature of the theme I’m using but any help is greatly appreciated.

You can see the different sizes here on the site: https://www.thetokyoblonde.net/blog

Cheers!