How Your Suit Should Fit – Essentials
Lapels:
Be conscious of the ties you'll be wearing with your suit. Lapel width should correspond to tie width.
Darts:
To avoid a boxy silhouette your suit should dart in at the waist. Even on a pre-darted suit, you should have your jacket tailored to fit your body. The thinnest point should be around the jacket's main button.
Sleeve Length:
The back of the sleeve should just meet the bump on the pinky side of your hand, and should allow 1/2″ of shirt cuff to show.
Pleats:
Flat front shown here, but if you opt for pleats, you must wear your pants on your waist, not on your hips, otherwise you risk bulging.
Cuff:
A classic look and a matter of preference. Cuffs look great with pleats. No cuff shown above.
Shoulders:
When you try a jacket on, you are really checking to see if it fits in the shoulders. It is one of the few alterations that is too expensive to be worth it. The seam should rest naturally on your shoulder. Lean against a wall: if your jacket touches first, it's too big.
Armholes:
If your armholes are too low, your whole suit will move when you stick your arm out. Opt for the modern, less boxy high armhole cut.
Buttons:
If your buttons look like they're pulling, the jacket is too small. If you pull the bottom of the V straight out, it shouldn't come out more than about 2 inches. If it does, it's too big.
Jacket Length:
With your arms at your side, curl your fingers up. Your jacket should be resting in your hand. A suit jacket should cover most of your pants zipper and all of your butt.
Pant Leg:
Suit pants will rarely fit off the rack. They're cut long, intended to be tailored. Opt for a modern, straighter cut that will create a sleek silhouette, instead of a frumpy, baggy one.
Break:
Where the pants fold when they meet your shoe is called the “break.” The pants should have one break at the bottom, and the leg should stop halfway down your shoe. This is known as a “medium break.” While a personal preference, short is high fashion, and is hard to pull off, and too much break can look baggy.