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 - Light Blue Heather1828.5
Adult Medium - Light Blue Heather2030
Adult Large - Light Blue Heather21.530
Adult XL - Light Blue Heather23.532.5