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)
Youth Small (5-6) - Sky Blue1722.5
Youth Medium (7-8) - Sky Blue1824
Youth Large (10-12) - Sky Blue1925.5
Youth XL (14-16) - Sky Blue19.526