Baby

Size (cm)	0-3	3-6	6-12	12-18
Width	21	22	24	25.5
Height	39	42.5	46	50

Size (inch)	0-3	3-6	6-12	12-18
Width	8.2	8.6	9.4	10
Height	15.3	16.7	18.1	19.6

To get good measurements, lay the shirt (preferably the one you love) on a flat, hard surface, then if there are any creases, smooth them out as much as possible

Width: place the ruler from the bottom of the sleeve and measure the width stopping under the other sleeve.

Height: measure from the highest point of the shoulder (top of the collar) to the bottom of the shirt.