How to center the form

I want the form to be centered completely

NOT the button

NOT one single field

NOT one label

I want the WHOLE form to be centered. THE WHOLE!!!

I don’t want to install any extra plugins for this.

The default visual page editor should be able to handle it. But it isn’t.

The pure left aligning looks shitty on my page.

I have trying now for hours. But all answer refer to the form elements to be centered.