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 - Red Heather17.525.5
Adult Medium - Red Heather19.528
Adult Large - Red Heather2230
Adult XL - Red Heather2531
Adult 2XL - Red Heather25.532