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)
Girls XS (4) - Light Navy11.2518
Girls Small (5/6) - Light Navy11.5018
Girls Medium (7/8) - Light Navy1219
Girls Large (10/12) - Light Navy
Girls XL (14/16) - Light Navy