Small fit to actual body chest = 37-38 inches
Medium fit to actual body chest = 38-39 inches
Large fit to actual body chest = 39-41 inches
XL fit to actual body chest = 41-43 inches
2XL fit to actual body chest = 43-45 inches
3XL fit to actual body chest = 45-47 inches
4XL fit to actual body chest = 47-49 inches