What is important is the position of your hips relative to the cranks and it is different for everyone. I want to have my weight on the saddle so that when pedaling and in the saddle as much leg power as possible goes into the forward motion of the bike. I need to adjust the fore and aft position and the height of the saddle to get into the sweet spot for me and it is different for every bike I have owned. I know the distance from the front of the saddle to the rear of the handlebar stem and that is a starting point. Particularly when pedaling up a hill it is obvious to me if the saddle position is not optimal and I will take hex wrenches so I can make small adjustments as I go with a new bike or a new saddle.