It depends on if I'm using it on my lap or on a desk/table, but usually between 18" and 24". It does help that I've had PRK, so I have 20/20 vision, despite being in my 40s. (It was 20/15 when I got it done 7 years ago, but it's slipped a little since then.) Certainly people with vision problems might not be able to work comfortably on a 13" screen.