Regatta Mens Jacket sizes????

[ha-ya-said-what]

Just need to know do the sizes Regatta jackets run big, run small or are they exact.

Ordering a custom embroidered jacket so need a rough idea on them! The Bf has like 3 dif sizes in clothes so impossiable to get an exact size off them............. his brother was no help cos he's bigger!! And please don't say "just ask him", it's not exactly a Christmas surprise if I go asking him cos he'll know right away am up to something and getting something made!