Fatso

Make use of the space that Gutenberg has been given.

Why is Gutenberg so narrow and does not make proper use of the space it’s been given in the admin? This plugin simply makes Gutenberg wider and thereby better. It gives you the freedom of working with blocks in the size you want, no longer restricting you to a paltry 610 pixels.

If you want a specific size of the content in the editor there is also a settings page for that!

For an even better experience in Gutenberg, use together with Welcome to the block editor B gone and Fullscreen mode B gone.