Take a tape measure to a good dealer and DON'T buy online.One firm's 8 is another firm's 5.Replicas made in the East ("Foreign,round eyed devils want little numbers sewn inside neck of jersey.") can be really crazy with size 4 being bigger than size 8. Santini come up small as do most Italian items.Belgian makes come up larger.
What I'm TRYING to say is buying a Jersey without measuring both you and the jesey is not a good idea unless Arnold Schwarzenegger and Wee Georgie Wood have not been catered for on next Christmas' gift list!