Sticky Nav Align with WP Admin Menu?

I have a sticky nav that I want to stay at the top of visitor’s screens. However, If I position it using margin-top so that I as admin can see the sticky nav *and* the wp admin bar, it appears lower for non-logged-in users.

How do I position the sticky nav so that it appears at the top of my browser window, no matter if the wp admin menu is or isn’t there?

Thanks.