Width is measured across the chest below the sleeves from seam to seam. Height is measured from the bottom of the shirt to the highest point on the shoulder (where the seam meets the neck).

Please note that each product has its own specific sizing chart.
SizeWidth (inches)Height (inches)
Adult Small - All Over Print1827.5
Adult Medium - All Over Print1928.5
Adult Large - All Over Print21.530
Adult XL - All Over Print2431
Adult 2XL - All Over Print25.531