The sizing chart refers to actual body measurements in inches.
Garment measurements are larger to allow 'EASE' of fit.         

YOUTH	S	M	L	XL
T-Shirt (chest)	26"-28"	28"-30"	30"-32"	32"-35"

ADULT	S	M	L	XL	2XL	3XL	4XL
T-Shirt (chest)	32"	36"	40"	44"	48"	52"	56"