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 Heather1827.5
Adult Medium - Red Heather1827.5
Adult Large - Red Heather20.530
Adult XL - Red Heather2129
Adult 2XL - Red Heather2329