What is the standard wardrobe depth and the best internal layout?

A wardrobe carcass is normally 600 mm deep, which clears a coat hanger on a standard rail; where space is tight, 550 mm works with a front-to-back rail, and 450–500 mm suits sliding-door units. Internally, plan in zones: long-hang for coats and dresses, double-hang for shirts, shelves for knitwear, and drawers at waist height for small items. Design around what you actually own, not a catalog photo.