What gun calibre would an Imperial Star Destroyer carry if its weapons scaled like those of a battleship?
Short answerAbout 96 inches by a simple length ratio, although the result is only a scale analogy.
NotesAn Imperial Star Destroyer is about 1.6 kilometres long, compared with a representative battleship length near 250 metres. That makes the fictional ship roughly six and a half times longer. Scaling a fifteen-inch battleship gun by the same ratio produces a weapon near 96 inches in calibre, with a projectile compared to a semi-truck. The calculation is a size analogy rather than a claim about how the fictional weapon works.