Ask how should a sweater fit and you will get two answers, both wrong. One says a sweater should be close to the body. The other says it should be relaxed. Neither is a rule, because a fine-gauge merino and a heavy lambswool are not the same garment and should not sit on you the same way. What does hold across every knit is where the four fixed points land: the shoulder, the body, the sleeve and the hem. Get those right and the weight of the knit decides the rest.
The shoulder seam is the one that cannot be fixed
The seam joining sleeve to body should sit at the outer edge of your shoulder bone, where the flat top of your shoulder starts to turn downward. Not past it. A seam that has slid onto your upper arm makes the whole garment read as borrowed, and it drags the sleeve length out with it.
This is the measurement to be strict about, because it is the one a tailor cannot cheaply correct. Taking in a knit body is straightforward; moving a shoulder seam means rebuilding the garment. If the shoulder is wrong, the size is wrong — no amount of liking the colour changes that.
Raglan and drop-shoulder knits are the exception, since they have no seam at that point by design. For those, check instead that the widest part of the sleeve sits roughly level with your armpit rather than halfway down your ribs.
Are sweaters supposed to fit tight?
No — but they should not be loose through the body either. The test is simple: with your arms down, you should be able to pinch about two to four centimetres of fabric at either side of your waist. Less than that and the knit will pull horizontally across your chest and show every ridge underneath. More and it starts to look like it belongs to someone else.
Gauge changes the target. A fine-gauge knit like The Quarter-Zip Knit is built to sit close, because its whole job is to go under a jacket without bunching at the armhole — aim for the lower end of that range. A heavier crew such as The Alpine Crewneck is meant to be worn as the outer layer as often as not, and needs the upper end so it drapes rather than clings.
One thing worth knowing: a knit that feels perfect in a fitting room after two minutes will relax slightly with body heat and wear. If it is snug at the moment of trying it on, it will not stay that way.
Is it better to size up or down in sweaters?
Size to your shoulders, then judge the body. That is the honest answer, and it usually means staying at your normal size rather than moving in either direction.
People size up for the wrong reason — they want room for a shirt underneath, panic in the mirror, and take a full step. A full size adds width at the shoulder too, which is exactly where you did not want it. If you plan to layer, try the knit over the shirt you actually wear, not over a bare torso, and you will usually find your normal size already accommodates it.
Sizing down is defensible in one case only: a deliberately oversized cut where the maker has already added ease, and you want it closer to standard. The Vesper Sweater is cut relaxed by design, so the size that skims you is a legitimate choice rather than a compromise.
Where you genuinely do want a step up is over another knit. A blazer or jacket worn over a fine-gauge sweater needs a few centimetres of extra chest room — covered in more detail in our guide to making a blazer look casual.
Sleeves and hem: the two that get ignored
The sleeve should end at your wrist bone, with the cuff sitting just past it. Slightly short is recoverable — push it up and it reads as intentional. Too long is not: a cuff swallowing your hand undoes an otherwise good fit, and knit sleeves cannot be shortened without losing the ribbing.
The hem should land somewhere between your hip bone and the base of your zip. High enough to show the line of your trousers, low enough that raising your arms does not expose anything. A crew neck worn on its own can sit at the shorter end. A zip knit like The Willow Zip Knit benefits from a fraction more length, because an open zip visually shortens the body.
Check the ribbing itself while you are there. Cuffs and hem should grip lightly and spring back when stretched. Ribbing that stays splayed after you release it has already lost its recovery, and no amount of washing brings that back.
Are sweaters supposed to be baggy?
Only where the cut says so, and even then the fixed points still apply. An oversized knit still needs its shoulder seam within reach of your shoulder and its hem above mid-thigh; what changes is the room through the body. The failure mode is a garment that is simply too large in every direction at once, which is not oversized — it is the wrong size.
If you want the relaxed look deliberately, the cleanest way is to keep the volume on top and take it out below: a fuller knit over a slim trouser or a straight jean reads as a considered proportion. A fuller knit over a fuller trouser reads as neither.
A quick order of checks
Shoulder seam at the bone. Two to four centimetres of pinch at the waist, less for fine gauge and more for heavy. Sleeve to the wrist bone. Hem between hip bone and zip base. Ribbing that springs back.
Five checks, about a minute. They apply to a €38 crew and a €130 merino equally, and they are the difference between a knit that lasts several seasons in rotation and one that hangs unworn because something about it never looked right.