Garstar -
Its different for men and women and different sites will say slightly different things but roughly for women:
Essential fat = 12–15%
Athletes = 16–20%
Fitness = 21–24%
Acceptable = 25–31%
Obese = 32%+
My BF% is about 20 - 21% at the moment so its on the low end of "fitness". I am aiming to lower it to around 18% or so. I like working towards this as opposed to obsessing with scale weight!
Thats why when you do strength training the scale may stay the same for pure weight but your clothes get looser. Your BF% is dropping as your lean body mass increases