19 length from underarm to waist. 17 please measure a jumper that fits you.
Lay on flat surface and measure across, underarm to underarm, then double this number to give you the chest size. Then from underarm to the wrist edge, to give you the sleeve length.
Then from underarm to waist hem to get the length. If the two measurements differ, it will give you a looser fit or more fitted look.