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Down Jacket Buying Guide: Fill, Loft, Waterproofing and Wind

Fill power, fill weight, shell fabric, and construction — how to read a label and choose a jacket for your climate.

By Alex Carter  |  Published 2026-10-10  |  Seasonal Dressing  |  Updated November 2026

A good down jacket is one of the best purchases you can make for a cold climate — and one of the easiest to get wrong. Two jackets can look identical on a rack and perform completely differently in a January wind, because the difference is inside the jacket: how much down it contains, how well that down lofts, what the shell is made of, and how the jacket is constructed. This guide explains the four numbers and features that matter, how to read a label, and how to choose a jacket for your climate rather than for the shop display.

First, a definition. "Down" is the soft, fluffy underlayer from ducks or geese. It insulates by trapping air, not by being thick itself — the loft, or fluffiness, of the down creates thousands of tiny air pockets, and still air is what keeps you warm. "Feather" is different: feathers are the outer plumage, they are flatter and heavier, and they insulate far less well. Most jackets contain a mix of down and feather, and the ratio is printed on the label. A jacket labelled 90/10 contains 90 percent down and 10 percent feather; a jacket labelled 70/30 contains less down and will be heavier and less warm for the same weight. Our winter layering guide explains how a down jacket fits into a full cold-weather system.

Fill power: the loft number that matters most

Fill power is the most important number on a down jacket label. It measures how many cubic inches one ounce of down occupies when it is allowed to loft fully. A higher fill power means the down lofts more, traps more air, and insulates better for the same weight. It also means the jacket can be lighter and more compressible for the same warmth.

As a rough guide: fill power around 500 to 550 is entry-level — warm enough for mild winters and for jackets where weight does not matter. Fill power around 600 to 700 is good all-round quality, suitable for most cold American winters. Fill power around 750 to 850 is high quality, lighter and warmer, and typical of jackets designed for serious cold or for packing small. Fill power above 850 is premium, and you pay a premium for it. The difference between 600 and 800 fill power is real, but it is not magic: a jacket with 800 fill power and very little down in it can still be less warm than a jacket with 600 fill power and a lot of down in it. Fill power tells you about the quality of the down, not about how much of it there is. That is the next number.

Fill weight: how much down is actually in the jacket

Fill weight is the total weight of down inside the jacket, and it is the number that decides how warm the jacket actually is. Two jackets with the same fill power can have very different warmth if one contains twice as much down as the other. Unfortunately, many brands do not print fill weight on the label, and some print only the total jacket weight, which includes the shell, zips, and lining.

When fill weight is printed, use it. For a light winter jacket or a mid-layer, a fill weight of around 100 to 150 grams is typical. For a serious winter jacket in a cold climate, a fill weight of around 200 to 300 grams is typical. For extreme cold, fill weights above 300 grams are common. When fill weight is not printed, use the jacket's overall feel as a guide: a jacket that feels light and thin for its claimed temperature rating is probably under-filled, and a jacket that feels substantial and lofts up when you shake it is probably well filled. Hold the jacket up and look at the baffles — the sewn chambers that hold the down. If the baffles look flat or empty, the jacket is under-filled. If they look full and puffy, the jacket is well filled.

Be sceptical of temperature ratings. There is no universal standard for the temperature a jacket is "rated to", and different brands test differently or do not test at all. A jacket that claims to be warm to minus 30 degrees may be warm to that temperature for a person who is active and layered, and not warm at all for a person standing still at a bus stop. Use fill power, fill weight, and the jacket's construction as your guide, not the marketing number.

Waterproofing, windproofing, and the shell

Down has a famous weakness: when it gets wet, it clumps, loses its loft, and stops insulating. That is why the shell matters so much. A down jacket's shell should be windproof, because wind strips warm air out of the down, and it should be at least water-resistant, because even a light rain or wet snow can soak through an unprotected shell.

Understand the difference between water-resistant and waterproof. Water-resistant means the shell sheds light rain and snow for a while; waterproof means it has a membrane or coating rated to withstand sustained rain. Most everyday down jackets are water-resistant, which is enough for commuting and town use. If you will be out in sustained rain or wet snow, look for a jacket with a waterproof membrane or a durable water repellent (DWR) coating, and check whether the seams are sealed. A jacket with a DWR coating will need that coating renewed over time — wash-in or spray-on DWR treatments are available and easy to apply.

Hydrophobic down — down treated to resist water — is a real improvement, and it is worth having if you live somewhere wet. It does not make a down jacket waterproof, but it keeps the down lofting longer when it does get damp, and it dries faster. It is a useful feature, not a reason to skip a proper shell.

The shell fabric also affects durability and weight. A heavier shell, around 30 to 50 denier, is more durable and more windproof but heavier. A lighter shell, around 10 to 20 denier, is lighter and more packable but easier to tear. For everyday use, a mid-weight shell is the best compromise. Check the zips: a good down jacket has a sturdy main zip, a storm flap or a covered zip, and zips that do not snag the shell fabric.

Construction: baffles, hoods, and cuffs

How a jacket is constructed decides whether the down stays where it should. The most common construction is sewn-through baffles, where the shell and lining are stitched together to create chambers. This is light and cheap, but it creates cold spots along the seams where there is no down. Box-wall construction, where the chambers have fabric walls, eliminates cold spots and is warmer, but it is heavier and more expensive. For most people, sewn-through baffles are fine for mild to moderate cold; for serious cold, box-wall construction is worth the extra cost.

Check the hood. A good hood should be adjustable, insulated, and large enough to fit over a hat. A hood that is too small or unadjustable is a decoration, not a feature. Check the cuffs: elasticated or adjustable cuffs keep cold air out. Check the hem: an adjustable hem or a longer cut keeps wind from blowing up the jacket. Check the pockets: they should be lined, warm, and positioned so you can reach them while wearing gloves. And check the fit: a down jacket should allow a layer underneath without being so loose that cold air circulates inside it. Try it on with the layers you will actually wear.

Down versus synthetic: when to choose which

Choose down if you want the warmest, lightest jacket for dry cold and you are willing to care for it. Choose synthetic if you live somewhere wet, if you will be active and sweating in the jacket, or if you want a jacket you can wash without thinking about it. Many people own both: a down jacket for cold, dry days and a synthetic jacket for wet or active days.

Care: washing a down jacket without ruining it

Down jackets need washing, but they need it done correctly. Wash a down jacket only when it needs it — typically once or twice a season — using a front-loading machine on a gentle cycle with a down-specific detergent. Do not use fabric softener, which coats the down and reduces its loft. Dry the jacket in a dryer on low heat with clean tennis balls or dryer balls, which break up clumps and restore loft. This takes a long time — often two to three hours — and the jacket must be completely dry before you store it, or it will smell and the down will clump permanently. Never store a down jacket compressed for months: store it hung up or in a large breathable bag, so the down keeps its loft. Our clothing care guide covers storage for all winter clothes.

How to choose, and what to avoid

When you are choosing a down jacket, check the label in this order: fill power, down-to-feather ratio, fill weight if it is printed, and shell fabric. Then check the construction: baffles, hood, cuffs, and zips. Then try it on with your winter layers and move in it. A jacket that passes all of those checks is worth its price; a jacket that fails the label check is not, however good it looks.

Avoid three traps. The first is buying a jacket for a temperature rating rather than for its fill numbers — the rating is marketing, the fill numbers are physics. The second is buying a fashion down jacket with a thin shell, flat baffles, and a low fill weight, which will look warm and feel cold. The third is buying a jacket that is too tight to layer under: a down jacket needs room for a sweater, and a jacket that only fits over a T-shirt is a jacket for a mild day, not a winter. For the layering system that goes under the jacket, see our winter layering guide and our climate dressing guide.