The Fit Guide: Suit Jackets
Words are fine and dandy, but there’s really one way to determine whether or not your clothing properly fits: trying it on.
Disclaimer: These rules are just "standards"—and no one has a "standard" body. Ultimately, the most important indicator of fit is how clothing looks and feels on you. Finding a fit that's right for you is more important than following the rules to a T.
Shoulders are make or break: there’s nothing a tailor can do about shoulders that don’t fit. You want the shoulders of the jacket to align as closely as possible to your own, without being too tight. To determine fit, grasp the fabric behind the armpit, right by your shoulder blade. If you can pinch between a half-inch and single inch of fabric you’re good to go.
A higher armhole makes for freer movement and an all-around sharper look. You should be able to grasp a full inch of fabric below each armhole.
You’re going to want a mirror or a very understanding friend for this one. Check to see if the fabric is straining anywhere on your back, particularly around the shoulder blades. Make sure it’s not hanging off of you like a sack of potatoes, either: this is often a problem for guys with curved backs. The fabric should fit the slope of the back, and fall flat without straining (note: a very small amount of strain is acceptable in slimmer fits).
Chest and Midsection
The jacket should be fitted around your chest and waist, but not so tight that it causes your lapels to “bow,” or stick outward. Lapels falling flat? Great. Next, you’ll want to see if you can slip one hand, Napoleon-style, below your lapel as if reaching into your pocket. If you’re able to imitate the first Emperor of the French without discomfort, you’re looking good.
Your sleeves shouldn’t look baggy, and they shouldn’t be long enough to completely cover your wrists. To test this, put on a shirt that properly fits you (more on that here). Your shirt sleeve should be a quarter inch to a half inch longer than your jacket sleeve, exposing a bit of shirt fabric.
Rules on length aren’t as set-in-stone as others—they can vary based on the height of the wearer. A happy medium is whether the jacket covers three-fourths of your seat.