A vest solves a specific problem: you want another layer, but not sleeves, and not the bulk that comes with them.
The vest went away for about a decade and came back as one of the more useful things in a cold weather wardrobe. It is the only layer that adds warmth to the core and structure to the shoulder without putting anything on the arms, which means it goes over a knit without the bunching that a jacket produces.
It also answers a specific problem in the transitional months. You are cold through the body and fine in the arms, and a coat is too much. That is a narrower problem than it sounds, and it covers about eight weeks of the year at each end of winter.
The Four Kinds
The Tailored Vest
Cut like the top half of a suit jacket. Lapels or a V neck, buttons down the front, often with a tie or buckle at the back. The sharpest of the four and the only one that reads formal. Worn over a shirt it is as close to a blazer as you get without sleeves, and it works in most offices.
The Knit Vest
A sweater without arms, in anything from a fine gauge to a chunky cable. Reads soft and collegiate. Layers beautifully over a shirt with the collar and cuffs showing, which is the whole look.
The Quilted or Padded Vest
Insulated, usually with a zipper front. Genuinely warm and genuinely casual. The most practical and the least dressy.
The Long Vest
Hitting mid thigh or lower, usually unfastened. Behaves more like a sleeveless coat. It adds a strong vertical line, which is its main job, and it layers over almost anything.
Sizing, Which Is the Part People Get Wrong
A vest is almost always worn over something. That sounds obvious and it is routinely forgotten at the point of purchase, where it gets tried on over a thin top.
Try it on over the thickest thing you intend to wear underneath. A tailored vest sized over a T-shirt will not close over a knit, and a knit vest sized over a bare arm will pull across the back when there is a shirt beneath it.
The place it shows first is the armhole. A vest armhole has to clear the sleeve of whatever is underneath without gaping. Too tight and the sleeve bunches; too loose and you see the shirt through the gap at the side.
The second place is the shoulder. On a tailored vest the shoulder seam should sit on the edge of your shoulder, same as a jacket. On a knit vest a dropped shoulder is normal and fine.
Length and Where It Ends
A vest creates a horizontal line at its hem, and where that line falls changes the proportion of everything below it.
At the waist. Shortest, sharpest, and best over a high waisted trouser or skirt, where the two lines agree.
At the hip. The standard. Neutral and easy.
Below the hip. Covers the seat, which some people want. It shortens the visible leg, so it wants height in the shoe or a longer line underneath.
Mid thigh and longer. Now it is doing the job of a coat and should be treated as one.
Try it on over the thickest thing you plan to wear underneath. A vest sized over a T-shirt will not close over a knit.
What Goes Underneath
The layer below is the one doing the visible work at the arm, so it should be worth looking at.
A shirt. The classic pairing with a tailored or knit vest. Collar out, cuffs showing. A good blouse does the same thing with more softness.
A fine knit. Works under anything except a tailored vest cut close, where it adds just enough bulk to spoil the line.
A long sleeve tee. The casual answer, and the right one under a quilted vest.
A dress. A knit or long vest over a long sleeve dress is one of the easier ways to get a third layer into an outfit without a coat.
Fabric, and How Warm It Actually Is
A vest covers the torso, which is where most body heat is lost, so it does more than its size suggests. How much more depends entirely on the cloth.
Wool and wool blend. The warmest for the bulk, and the only one that holds a tailored shape properly. Worth the money in a tailored vest.
Cotton knit. Breathable, light, and more about the layer than the warmth. Right for the weeks either side of summer.
Quilted synthetic. The warmest of all and the bulkiest. Compresses for packing, which is why it travels well.
Faux shearling and borg. Very warm, very casual, and visually bulky. It adds width at the shoulder, so it suits a narrow leg underneath.
Three Outfits
To work. Tailored vest, shirt underneath with the collar out, a straight trouser, a loafer. The vest is doing the job a jacket would and the room stays warmer.
Weekend. Knit vest over a shirt, straight jeans, a flat boot. Roll the shirt sleeves.
Cold and practical. Quilted vest over a mid weight knit, a trouser with some structure, a boot with a sole. This is the combination that actually gets worn in November.
The One to Avoid
A vest over nothing, in a fabric that was designed to go over something. A tailored vest worn as a top can work when it is cut and lined for it, with a finished armhole and a closed front. The same vest bought as part of a suit and worn bare tends to gape at the arm and show the lining, and it reads as a missing shirt rather than a choice.
Four Checks
Armhole depth. Raise your arms. The vest should stay roughly where it is.
The back. Tailored vests often have a tie or buckle at the back. It should be adjustable and it should be flat enough to disappear under a coat.
Button spacing across the chest. The same gap problem a blouse has across the bust, and the same fix.
The hem shape. A pointed hem at the front sits differently from a straight one and reads a little more formal.
Vests to Consider
The Short Version
Pick the kind by the job: tailored for an office, knit for ease, quilted for warmth, long for a vertical line. Size it over the thickest thing that will go underneath and check the armhole clears the sleeve. Decide where the hem lands, because that line changes the proportion of everything below it. Then put something worth seeing on the arms, because that is the part the vest leaves on show.