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)
Infant 12M - Oxford Grey9.512
Infant 18M - Oxford Grey1114
Infant 24M - Oxford Grey1114.5
Infant 6M - Oxford Grey812