How to choose a men's sweater?

A $40 sweater bought in October that pills under the arms by week three, goes slack at the cuffs and ends up at the back of a drawer before Christmas: it's the most common story, and it costs more than it looks. Choosing a men's sweater well doesn't take expertise. A label to read, a couple of checks in the fitting room, and a clear idea of what the sweater is for. The piece you'll wear most between November and March deserves those five minutes.

What to keep in mind before you buy:

• Fibre first: merino wool for everyday wear, lambswool for warmth, cashmere for softness.
• The neckline sets the use: crew neck for everything, V-neck over a shirt, turtleneck instead of a shirt.
• The gauge (how fine the knit is) tells you whether it goes under a jacket or is worn on its own.
• A well-made sweater costs roughly $80 to $180, and lasts five winters.
• The ribbing gives quality away: it should spring back when you stretch it.

Which fabric is best for a men's sweater?

The diameter of the fibre, measured in microns, explains why one wool itches and another doesn't. Below about 20 microns, most skin stops noticing. Cashmere sits around 15 to 16 microns, fine merino between 17 and 21, lambswool and Shetland well above.

Our advice for a first purchase: merino. It can be worn next to the skin or over a T-shirt, doesn't hold odours (a night airing out often replaces a wash) and goes in the machine on a cold wool cycle. Lambswool comes second, for a thicker sweater you pull on on Saturdays.

Cashmere needs a word of caution. A $70 sweater sold as "cashmere" is often a low-percentage blend or a short fibre that fuzzes quickly. Proper two-ply starts around $170. We've put together a full ranking of the best cashmere sweater brands for men, with price and composition benchmarks.

As for the label, it is regulated. In the United States, the FTC rules under the Wool Products Labeling Act require wool garments to show their fibre content by percentage of weight. Read it before the price tag.

Crew neck, V-neck or turtleneck: which neckline?

The neckline decides what goes underneath, and therefore where the sweater will get worn. A man who owns only one sweater should pick the crew neck.

The crew neck does it all

Wear it on its own, over a white T-shirt showing a sliver at the collar, or over a button-down shirt with only the collar peeking out. Choose a neckline that hugs the base of the neck without squeezing: too wide and it sags within two seasons.

The V-neck goes over a shirt

The V-neck was designed to frame a shirt, with or without a tie. Keep the V moderate, stopping at mid-chest. Any deeper and it looks straight out of the late nineties. Over bare skin, it doesn't work.

The turtleneck replaces the shirt

It does the job of a shirt and tie in one move, under a blazer or an overcoat. It needs a fine knit and a collar that stands up on its own. Our guide on how to wear a turtleneck for men covers the fibres and the pairings.

Quarter-zip and cardigan

The quarter-zip (a zipped or buttoned stand-up collar) looks sporty and protects the neck under a leather jacket or a bomber. The cardigan opens and closes with the temperature: the most versatile of the lot, best treated as a light jacket.

Gauge and weight: fine knit or chunky knit?

Gauge is the number of needles per inch on the knitting machine. The higher it is, the finer the knit. It rarely appears on the label, but you can see it.

• 12 to 16 gauge: very fine, almost smooth. Slips under a suit jacket or blazer without bulking up the shoulders.
• 7 to 9 gauge: medium knit, the everyday sweater, warm enough to go out without a coat at 50°F.
• 3 to 5 gauge: chunky knit, wide ribs or cables. Worn alone or under a roomy coat, never under a fitted jacket.

One simple rule: the more structured the layer on top, the finer the knit should be. A chunky cable knit under a blazer pulls at the buttons and bends the lapels. Men with broad frames should also go easy on heavy cables, which add volume to the chest.

How should a men's sweater fit?

A sweater that fits badly can't be saved, not even in the finest wool. Four checks are enough, standing still and then with your arms raised.

1. Shoulders: the armhole seam sits at the end of your shoulder, not an inch down your arm.
2. Length: the hem stops at the belt or just below, covering the buckle without reaching the hips.
3. Sleeves: they end at the wrist bone, without bunching over the hand. The cuff should hold the sleeve when you push it up.
4. Ease: pinch the fabric at your side. About an inch on each side for a sweater worn under a jacket, a little more for a weekend one.

Torn between two sizes? Go smaller for a fine knit and larger for a chunky one, which tends to tighten after the first wash. Raise your arms: if your stomach shows, it's too short.

How to spot a well-made sweater

A few checks, a minute in total, reveal how much care went into making it.

Stretch the cuff ribbing a couple of inches, then let go: it should snap back at once. Ribbing that stays open will be open for good after three wears. Then hold the sweater up to a light. A dense knit lets little light through; a sparse one means a cold sweater that loses its shape.

Look at the shoulder seams. On fully fashioned sweaters, each panel is knitted to shape, and you can see small fashioning marks along the armhole. The panels are then linked stitch by stitch, which gives flat, supple seams. Cut-and-sew sweaters, cut from knitted fabric like a T-shirt, have bulkier seams. Fully fashioned knitwear ages better.

Last test: crush a sleeve in your fist for ten seconds. Good wool springs back without holding creases.

How much should you spend on a good sweater?

The best men's sweater isn't the most expensive one, it's the one you wear for four winters without it losing shape. Under $40, pure wool in a decent knit is very hard to find: you're mostly paying for acrylic. Between $80 and $180, you get well-knitted merino or lambswool, which is enough for most men. Above that, you're paying for cashmere, alpaca, European or Scottish manufacturing, or a label.

Do the cost-per-wear maths. A $120 merino sweater worn twice a week for five months, five winters running, comes to about 55 cents a wear. The $35 acrylic one abandoned in December costs well over two dollars each time it was worn.

Which colour should you buy first?

Your first three sweaters should come in shades that go with everything: navy, heather grey and ecru. Navy works with jeans and with khaki chinos, heather grey with any trouser colour, ecru brightens winter outfits that tend to run dark. Then come bottle green, camel and burgundy.

We advise against black for a first everyday sweater. It shows every bit of lint and hardens the face in winter light. Save it for a fine turtleneck in the evening. To go further with combinations, our method for matching colours in an outfit comes down to a few rules.

What to wear with a sweater

A sweater works with almost everything below the waist, as long as the textures agree. A grey lambswool crew neck with raw jeans and leather boots: the safest weekend outfit there is. A navy merino over a white oxford shirt and khaki chinos, for a tieless office day. A bottle-green Shetland with brown corduroy trousers, for November Sundays.

In the cold, the sweater becomes a layer. Under a wool overcoat or a peacoat, a medium knit is enough; under a parka, the chunky knit finds its place. Never stack two heavy knits.

The mistakes that shorten a sweater's life

Hangers first. Knitwear on a hanger stretches at the shoulders and forms two bumps you'll never get out: fold sweaters flat on a shelf. Washing too often comes next. Wool needs washing after five to eight wears, not after every day; in between, a night over the back of a chair airs it out.

To wash, cold water, wool cycle, low spin, dry flat on a towel, away from the radiator. Never the dryer. Remove pills gently with a fabric shaver. In spring, store your sweaters clean (moths go for stained fibres) in a box with a cedar block or a lavender sachet.

One last piece of advice, and it applies to the whole menswear wardrobe: buy fewer, buy better. If you only buy one sweater this winter, make it a navy merino crew neck, 12 gauge, in your exact size. It will work under a jacket, with good men's jeans, at the office and on weekends, and you'll finally see what a good sweater does for an outfit.