The best way to measure your correct size is to compare it to a similar garment you already own. Lay that garment flat and take all measurements from the outside.

 

All measurements in inches.

Size	Chest	Length	Sleeve
S	21	27	8.5
M	23	28	9
L	25	29	9.5
XL	27	30	10
2XL	29	31	10.5