I'm building a responsive website and I'm wondering what unit I should use? I've seen a lot of sites using pixels (px) for measurements and I've seen some using percent (%). Is there a preferred — or right — way of doing responsive design? 

I've found percent to be hard to use, since it makes calculations hard and I've ended up with values like 2.754% and so on when setting widths/margins etc. Pixels seems easier, it's just simple addition and subtraction, but I've read that it isn't "future proof" or something like that and wont scale properly if the user zooms in the browser window. Is that still true?

If you have any experience or expertise, please share! I would love to hear what you guys have to say!

Thanks!