T shirts are measured armpit to armpit for Width, collarline to hem for Length.
Size Width Length
S 17.5 inches / 45 cm 23 inches / 58.5 cm
M 19 inches / 48 cm 24 inches / 61 cm
L 21 inches / 53.5 cm 25 inches / 63.5 cm
XL 22 inches / 56 cm 26 inches / 66 cm