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 - White1727.5
Adult Medium - White1930
Adult Large - White2128
Adult XL 21.5029.50
Adult 2XL 24.5031
Adult 3XL 25.5032.50