A well-fitting trench coat for women should have shoulder seams that align with the natural shoulder line, allowing for comfortable movement. The sleeves should hit at or slightly below the wrists when the arms are resting by the sides. The length of the trench coat can vary, but a classic length falls just above or below the knee. The coat should have enough room to layer comfortably over clothing without appearing too tight or too loose. The belt should sit at the natural waistline, accentuating the figure and creating a flattering silhouette.