Menu Button right aligned

What custom CSS code do i need to make sure that, whatever size i make my browser window, my menu button stays right aligned?

As of now if the window is wide you actually see the full menu but as you make it more narrow the button goes to the right, then tighter…it goes to the left…then tighter it goes to the right.

Example- on an iphone the menu button is right aligned
on a IPAD the menu button is LEFT aligned and messes with the alignment of the header

Thanks!