Unisex Classic T-shirt: The answers are the ancestors

Size (cm)	S	M	L	XL	2XL	3XL
Width	50	53	56	59	62	65
Height	70	72	74	76	78	80

Size (inch)	S	M	L	XL	2XL	3XL
Width	19.5	21	22	23.5	24.5	25.5
Height	27.5	28.5	29	30	30.7	31.5

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.