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 - White17.527.5
Adult Medium - White1929
Adult Large - White21.530
Adult XL - White2430
Adult 2XL - White2530.5