The size tag says M (8/10), but because this is vintage sizing, please check these measurements against a favorite garment at home. Taken with the sweater laying flat:
Chest (from armpit to armpit): 13 inches
Length down center back (from base of collar at neckline to bottom of hem): 17 1/2 inches
Length of sleeve from armpit to cuff: 16 inches unrolled
Shoulder to shoulder across the back: 11 1/2 inches
From a smoke-free home.