A blazer can look expensive on the hanger and cheap on the body, and the gap between those two outcomes is almost never the fabric or the price tag. It is fit. Jackets are the most engineered garment most people own: canvassing, shoulder padding, armholes, button stance, vent construction. Each of those elements has a correct relationship to a specific body, and each one fails in a predictable way when it is wrong. The failures are visible from across a room, long before anyone reads the label.
Most of these mistakes can be caught in the fitting room in under ten minutes, before money changes hands. What follows is a walk through the ones that matter most, in roughly the order a jacket reveals them.
The Shoulder Seam That Sits Past the Bone
The single most expensive mistake in a blazer is a shoulder seam that hangs beyond the edge of the shoulder bone. Look at the outer point of the shoulder in a mirror, then find where the sleeve attaches. On a jacket that fits, that seam lands close to the bone, maybe a half inch past it. When it drops an inch or more, the sleeve head collapses into a soft fold, the whole silhouette slumps downward, and the wearer looks like a child in a borrowed jacket.
This cannot be fixed. Shoulder width is set by the jacket's construction, and a tailor who offers to narrow it is quoting a rebuild that costs more than most off-the-rack jackets. A jacket with a shoulder that is too wide is a jacket to put back on the rack, regardless of how good the color looks.
The opposite error is subtler. A shoulder seam that bites into the bone, pulling the sleeve upward and creating a dimple at the top, means the jacket is too narrow. Some men tolerate this because the chest looks sharp, but the dimple never relaxes and the armhole will restrict every forward reach. Both directions of error announce themselves in the mirror within seconds.
Armholes Cut for a Mannequin, Not a Body
Low armholes are the quiet epidemic of mass-market tailoring. A jacket with a deep armhole lets the whole sleeve move as a unit with the torso, which means lifting an arm drags the entire jacket upward and the lapels lift off the chest. Reach across a table and the jacket rides up around the ears.
The test is simple. Button the jacket and reach forward as if to shake a hand. A high armhole keeps the jacket anchored at the waist and lets the arm move independently. A low one turns the jacket into a cape. The difference is obvious the moment the arm crosses the body, and it cannot be tailored away; the armhole is cut into the pattern.
High armholes feel slightly snug when the jacket is first tried on, which scares off buyers who mistake restriction for bad fit. That initial tightness is the price of a jacket that moves properly, and it relaxes with wear.
The Button Stance and the Waist Suppression Trap
Button stance is where the jacket's top button sits relative to the waist. A low stance lengthens the torso visually, which flatters short men and men with long legs. A high stance shortens the torso and can make even a tall frame look blocky. The mistake is buying a jacket whose stance fights the wearer's proportions because the rest of the fit is good.
Waist suppression is the related trap. A jacket nipped in hard at the waist creates a dramatic V, and on the right frame it looks athletic. On a heavier midsection, aggressive suppression pulls the front panels apart and creates an X-shaped wrinkle radiating from the button. That wrinkle is the jacket announcing that it is fighting the body underneath. A gentler suppression, or a single-breasted jacket with a softer line, will hang cleanly.
Sleeve Length Measured by the Wrong Landmark
Sleeve length has one reliable landmark: the wrist bone. A jacket sleeve should end there, showing roughly a quarter to a half inch of shirt cuff when the arms hang naturally. Sleeves that stop at the base of the thumb are too long and swallow the hand. Sleeves that leave the entire cuff exposed and stop well above the wrist look shrunken.
This is one of the few blazer errors that a tailor can actually fix, usually for a modest fee, because the sleeve can be shortened at the cuff. The catch is functional buttons. Working buttonholes on the sleeve make shortening far more expensive, since the tailor has to move the buttonholes up and re-finish them. A jacket with working cuffs that is otherwise perfect is worth buying only if the sleeve length is already close.
The Jacket That Cannot Close Without a Gasp
A blazer should button without strain and without a visible pull across the chest. The classic test is to button the jacket and slide a flat hand between the chest and the fabric. If the hand does not fit, the jacket is too tight through the chest. If two hands fit easily, the jacket is too loose and will look like a sack from the side.
The chest measurement matters more than the labeled size, because vanity sizing has made a 40 in one brand roughly equal to a 42 in another. A jacket that pinches at the button and creates horizontal pull lines is not going to break in. It will simply strain every time it is worn, and the strain shows in photographs.
There is also a posture component. A jacket cut for a man with a flat back will gap at the collar on a man with a slight stoop, and no amount of chest measurement will fix that. The collar gap is its own separate problem, covered next.
The Collar Gap Behind the Neck
Turn sideways in the mirror and look at the space between the jacket collar and the back of the neck. A well-fitted jacket collar sits flush against the shirt collar with no daylight visible. A gap of even half an inch means the jacket was cut for a different posture, usually a straighter back than the wearer has.
A collar gap is stubborn. Tailors can sometimes adjust it by taking in the back seam, but the fix is fiddly and not always successful, because the problem lives in the relationship between the collar and the shoulder line. A jacket with a persistent collar gap will always look slightly off from behind, which is exactly the angle most people see in a meeting room.
Vents That Flare When Standing Still
Side vents on a blazer should lie flat when the wearer stands with hands at the sides. If they flare open, the jacket is too tight across the hips. If they overlap and pucker, the jacket is too loose or the vent construction is poor. Center vents have the same rule but are less forgiving of hip width, which is why side vents are the safer choice for anyone with a fuller seat.
Vent flare is often the first sign that a jacket fits through the shoulders and chest but not through the hips, a common mismatch in ready-to-wear. A tailor can sometimes let out the side seams, but the amount of fabric available is limited, and a jacket with no seam allowance left is a dead end.
Length Judged by Fashion Rather Than Bone
Jacket length has drifted shorter over the past two decades, and the trend has convinced a generation of buyers that a cropped blazer is correct. The reliable landmark is the knuckles. With arms hanging naturally, the bottom hem of the jacket should land somewhere near the top of the hand, around the first knuckle. A hem that stops at the wrist bone is too short and will look like a bolero on a tall frame. A hem that reaches mid-thigh is too long and shortens the legs.
Short jackets photograph well on models with narrow hips and long legs. On most bodies they break the vertical line and make the torso look truncated. The knuckle test is not glamorous, but it is consistent across brands and body types.
Lapel Width Out of Step With the Frame
Lapel width cycles in and out of fashion, but the frame sets a floor and ceiling regardless of the decade. A narrow lapel on a broad chest looks like a ribbon. A wide lapel on a narrow chest swallows the torso. The practical range is roughly two and a half to three and a half inches at the widest point, with the wider end suiting broader builds.
The lapel also has to relate to the shirt collar and tie width. A wide lapel with a skinny tie looks like a mistake in both directions. This is a coordination issue rather than a pure fit issue, but it is caught in the same fitting room session and belongs on the same checklist.
Pockets and Flaps That Sit Wrong on the Hip
Flap pockets should sit roughly at the widest part of the hip and lie flat against the body. When the jacket is too tight through the waist, the flaps push outward and the pocket bags show through the fabric as bulges. When the jacket is too loose, the flaps hang away from the body and catch the light.
Patch pockets, increasingly common on casual blazers, have their own failure mode: a patch pocket that sits too low drags the visual weight of the jacket downward. The top edge of the pocket should align roughly with the bottom of the button stance, and any deviation of more than an inch reads as sloppy from a few feet away.
The Lining and Canvas That Announce Themselves
A cheaply constructed jacket makes itself known through the lining. If the lining ripples when the jacket is buttoned, it is cut too tight or attached without enough ease, and it will tear at the armhole within a season of regular wear. A fused front (glued rather than canvassed) can look crisp on the rack and then develop bubbles across the chest after a few dry cleanings.
The test is tactile. Pinch the fabric just above the top button and rub it between thumb and forefinger. A canvassed front has a slightly springy, layered feel. A fused front feels flat and stiff, almost like cardboard. Neither is automatically a dealbreaker at every price point, but a fused jacket at a canvassed price is a mistake worth catching before the receipt is signed.
None of these checks requires expertise, and all of them can be done in a fitting room with a mirror and five minutes of honest looking. The blazer that passes them will look better after five years than the one that failed them looked on the day it was bought.
