How should a well-fitted suit jacket look?
The shoulder seams should match the width of your shoulders, and lie flat when standing up straight. The two sides of the jacket should meet neatly in the front, and the buttons should close without strain or wrinkling across the waist. “A half-inch of linen” is a good rough guideline for how much of a shirt sleeve should be visible past the ends of a suit jacket sleeve. This measurement doesn’t have to be exact, so long as the jacket isn’t short enough to see the seam where the cuff meets the sleeve, or long enough to fully cover the cuff. The jacket length should be past the waist and sit around center-palm when your arms are relaxed at your sides.