Full Screen App plus Calculator or other apps

Whenever I have something full-screen on my Mac, it seems to slide the whole screen to the left and everything else is gone. I can switch back and forth with Ctrl-Left/Right. The problem is, for example if I'm full-screen in something like Safari and need the Calculator. I can launch with Mac+Space and type calculator, but it rotates the screen back to the desktop before launching - and I can't get the calculator to go to the same screen as Safari, so I end up having to toggle back and forth to do calculations. Is there some way to make an app launch over the full-screen safari so that I can see them both, even though Safari is full-screen behind the calculator?