that's a good question. get on a bike that you can stand over easily and put your hands on the hoods. Is it too far of a stretch? Your torso/arms are probably short.
I know my arms aren't short because if i put my arms out straight (crucifixion position) they measure from fingertip to fingertip more than my height.
SO... since I can straddle the bike and my arms aren't short it MUST be my torso.
We are probably perfectly proportioned, btw, but bikes are built for men who are built differently!