Because of their constricting fit, vests can be the most difficult part of a suit to tailor. Buying one with an adjustable strap will ensure that your vest does not become a one-time memory of your glory days hanging painfully in your closet.
At its shortest point on the bottom, the vest should completely cover the waistband and sit comfortably below the pant button but not so low that the points of the vest show beneath the jacket. At no point should the shirt be visible around the waistline when wearing a vest.
A well-fitted vest should be exposed about an inch or two above the jacket buttons; you can use your discretion as to how high you want to take this, but exposing too much shortens the length of the body and hides what we’ll assume is a great tie.
At the shoulders, the neckline should be wide enough that the vest does not cover the collar points or slip underneath them.
Like the shirt, the jacket’s shoulders should not extend beyond your own. If the shoulder padding touches the wall before your biceps do, the jacket is too big.
At the chest, the jacket should be loose enough that you can easily slide a flat hand in at the lapel without any strain on the fabric or buttons, but not so loose that you can fit a fist.
With the arms at the side, the back of the jacket cuff should rest on the base of the hand, just above the wrist; the inside cuff should never come in contact with the palm of the hand. The jacket should leave about half an inch to an inch and a half of shirt cuff exposed.
Assuming you have somewhat normal proportions, your knuckles lining up with the bottom of the jacket is an indicator of a proper fit. Ditto these buttons: the top button of the two-button suit or the middle button of the three-button suit should never fall below the navel.
With so many other things to worry about, pants are the easiest part of the suit equation. In the back they should hover around the top of your shoe sole and in the front break with about an inch covering the shoe. Tailored cuffed pants can create a stockier look on shorter guys, so if you’re under 5’9”, stick to un-cuffed pants.