Thanks for the comment. I should have specified that this suggestion is for men/boys and I agree that the ratio would be too fast for girls/women.
As I said,this is what I usually started with and then tweaked from that point, some a little faster, some a little slower.
My absolute best college guys would come through the 600 at 1:17 - 1:19; best HS 'ers at 1:22 - 1:25.
Of course my collegiate runners could run 46+/- and could handle the 49 - 52 range. The HS'ers were 48-50 range and could handle the 53-54 opener. Just as with all distances, the ratio was determined by age/experience/talent/mentality.
One of my best collegians was a 50 sec. 400 hurdler before I tried him on the 800. Another was 47 400 runner before changing. He could also run xc and a consistent 10.6 - 10.7 100 meters. They both became pretty fair 800 runners.
I trained them both differently because of their different talent(s).