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Down Jacket Fill Weight Explained in Detail

Fashion cloth winter dark green down jacket isolated on white background.

Down jackets are staple of outdoor gear, and can be used for everything from car camping to extreme mountaineering. Often, we look for down jackets and other down gear when we need it for demanding outdoor use, but they can be worn in any setting that asks for a cozy, warm jacket. Down jackets come in a variety of shapes and forms, and if you’ve been searing for one, you’ve probably started to hear the term “down fill weight,” but what does it mean?

Everything you need to know about down jacket fill weight and quality

Down jacket fill weight is a common term that refers to the relative warmth of a down jacket. It’s easy to think that this is the defining term, but it’s often less important than another, less memorable term: down fill power. In colloquial discussion, these terms are often thrown into one bucket together as “the down fill quality” of a piece of gear.

Down fill weight vs. down fill power

Down fill weight is simply the physical weight of the down fill within a piece of gear, while down fill power is a measure of the quality of the down fill.

Down fill weight

Down fill weight is the base weight of down fill that exists in a piece of gear. For a down jacket, fill weight typically ranges from 3 ounces to 6 ounces for standard lightweight and midweight gear. Heavier jackets, like specialized winter coats, can have even more.

The size of the gear itself influences how warm a certain fill weight will be — a jacket will be much warmer than a sleeping bag with the same fill weight, due to the fill being distributed over much more surface area. Down fill weight can be a useful measure, but not all manufacturers actually report it. If you see a weight listed on a down jacket, it’s most likely the net weight, not the fill weight.

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Down fill power

Down fill power is a measure of the quality of the down material in a jacket, as a function of the amount of loft the fill has. It’s calculated by how much space 1 ounce of down takes up in a cylindrical tube. For gear like down jackets, the range for down fill power is usually from 500 – 900, with the higher numbers representing gear that will provide more warmth.

Lower down fill power ratings can be found in casual jackets, but are rarely seen in outdoor gear. Conversely, fill power ratings above 900, up to 1,000, are sometimes found in extreme gear, usually targeted as ultralight. The down fill power number is a direct representation of its loft — the number of cubic inches one ounce of the down fill will reach when uncompressed.

The higher the loft, the lighter, warmer, and more compressible it is, which is why down with high fill power gets the highest material ratings.

Young woman yellow down jacket runs for daughter in red down jacket outside.

What makes a warm down jacket?

The actual warmth of a down jacket depends on both the down fill weight and fill power — that is, both the amount of fill as well as the quality of the fill. It’s easiest to compare jackets of either the same down fill weight or the same down fill power, at least when you’re just getting familiar with what these numbers mean and how they impact your gear.

To give you a starting point, a 600-fill down jacket with 6 ounces of fill weight will have twice as much insulation as a 600-fill down jacket with only 3 ounces of fill weight, making the first jacket quite a bit warmer.

Similarly, a jacket with 3 ounces of fill and a 600 fill power rating won’t be as warm as a jacket of the same weight, but with an 800 fill power rating. You can also find jackets that are the same warmth, but different balances of fill and weight. When this happens, the difference comes down to the overall weight and bulk of the jacket — the one with the higher fill weight will be bulkier, heavier, and less compressible.

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The warmest down jackets will have both high fill power and a relatively high fill weight — though that doesn’t necessarily mean the best performance, since one of the main factors in down gear is weight, particularly if it needs to be carried.

Higher down fill power or higher down fill weight?

Manufacturers will often optimize both of these for you, offering gear that falls into three performance tiers: lightweight, midweight, and high-performance or four-season (the third bucket has many names). This can be misleading, as these categories refer less to the weight of the products within them, and more to the performance value, lightweight being for less demanding use, midweight being for relatively casual use in colder conditions, and four-season being for use in demanding conditions.

There can be a fourth tier as well, for use in extreme conditions like specialized mountaineering). These tiers are a great starting point when picking a jacket. Within these tiers, you’ll still have options for down fill power and down fill weight within the same performance tier.

Your choice will depend primarily on your budget and whether or not you need to minimize weight.

Picking a down jacket for backpacking or mountaineering

The most common situation for quality down jackets is with backpacking, or any alpine activity that puts you in cold conditions, often where you’re carrying gear and needs to minimize weight. If you’re looking for gear that’s both lightweight and high-performing (warm), you’ll want to prioritize a jacket with a high fill power number. This will ensure your gear keeps you warm when you need it to, whether you’re backpacking overnight or skiing in a winter storm.

The fill weight is still a factor, especially if you’re carrying your gear as with backpacking, but the weight of a cooler jacket could be exactly the same as a warm one with a higher fill power. You can start by deciding what your max weight target is for a jacket, then find one that meets your needs for performance and warmth (keep in mind that the fill weight refers to only the down material and isnt’ the weight of the jacket, which also includes the weight of fabric and zippers). It’s also important to note that, generally, higher fill power ratings mean a higher pricetag.

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And with gear like down jackets, prices can add up very quickly, especially if you’re buying more than one item. If price isn’t an issue and your main priorities are warmth and weight savings (generally the two biggest factors for down fill gear), aim for the lowest down fill weight with the highest down fill power.

Best down jackets for casual use

Man wearing black down jacket.

If you’re looking for lightweight or midweight gear — to be used in summer months or casually around town — a high fill power is less important. A super high fill power could actually be entirely too warm for your needs! For down summer gear for backpacking, for example, where gear weight is a priority, your jacket doesn’t need to keep you warm in extremely low temperatures.

In this case, you can balance your warmth needs while maintaining the main priority of keeping weight low. Look for a low down fill weight, then find a fill power that meets your other needs. “Down sweaters” can be a great choice for this, as they minimize weight but still use high quality down, usually between 650 and 800 fill power.

For down jackets where weight isn’t an issue, like on day trips, climbing, or just hanging out, you don’t really even need to look at the fill weight. The fill power alone will what you need to know for warmth: the higher the fill power, the warmer the jacket.