I thought 1 1/4" was standard. Â And on RTW you pretty much see 1 1/2" Â I am shocked to hear talk about 1/2 an inch, that's practically on the end of the sleeve and looks ridiculous IMO.
Actually, 1 1/4" from the center of the last button to the edge of the sleeve is the old Savile Row standard. For most buttons, that means the edge of the button is about 7/8", maybe 3/4", from the end of the sleeve. That length is not supposed to be exceeded
. Too far from the edge looks a lot worse than too close.