Demystifying Down Fill Power

If you’re hunting for the best down jacket for a specific environment or activity, you’re probably nerding out on the down fill power ratings of dozens of very different down jackets. Well, either you’re nerding out, or your head is spinning.

550 … 800, 120g … 500g… What do all these “fill power” numbers really mean when it comes to a goose down jacket?

We’ll get to that. But first of all, it pays to learn a little bit about how down insulation works in the first place.

The benefits of down insulation

Despite the release of new, high-tech insulation technologies just about every season, good ol’ goose down is still one of the warmest, lightest and most-compressible insulation materials available. Considering the first commercially available down jacket was produced in 1936, that’s an impressive run. Outdoorspeople everywhere still stuff down jackets into backpacks before a trip mainly for the aforementioned three reasons: they keep you warm, they’re lightweight and they pack down to a very small size.

RELATED: How To Wash Your Down Jacket

So how does down insulation work so well? Down jackets keep you warm the same way goose down keeps geese warm—which is also the same way the newer synthetic insulation materials keep you warm. By trapping pockets of warm air close to the skin, keeping the warm air in and the cold air out.

But while synthetic insulation may outperform down in wet weather, down still comes in first in cold, dry environments. Also, down jackets almost always weigh less and compress more than their synthetic counterparts, providing the same amount of warmth at a fraction of the weight.

The Helium waterproof down jacket.

What do down fill ratings mean?

A higher down fill rating doesn’t necessarily mean one jacket will be warmer than another. The down fill rating number is a measurement of down quality, meaning the cubic inches of loft one ounce of the specific down produces. A higher rating means less down fill is required to capture the same amount of heat.

But that doesn’t automatically mean a 900 fill down jacket is warmer than a 650 fill down jacket. What you also need to take into consideration is the amount of down used in the jacket. For example, it’s possible to make a warmer jacket with a lower quality down simply by filling the jacket with more down. That’s where the down weight numbers—like 120g, 300g, etc.—come in to play. Jackets stuffed with lower-quality down are often less expensive than those filled with a higher-quality down, but they’re also heavier and less compressible.

Down jackets with a high fill power are usually lighter, less bulky and more compressible than jackets with a low fill power that are equally warm. But again, much depends on the fill weight. A 650 down fill jacket with 330g of down may be as warm as an 800 down fill jacket with only 120g, but the 650 fill jacket will be bigger, heavier and take up more room when stuffed in your pack.

RELATED: How To Layer With Down

The warmest down jackets are built with a high fill power down and a heavier down weight. But depending on where you’re headed and what you’re doing, you may not need all that warmth. For instance, if you’re planning to do a little twilight bouldering in your neighborhood park, you might need a lightweight down jacket to ward off the chills while you’re spotting your buddy. But you probably don’t need a down parka that could keep you toasty while establishing a new route in the Himalayas.

Outdoor Research Down Jackets

Whatever your down insulation needs, Outdoor Research makes the down jacket for you. (All Outdoor Research down jackets have been certified by The Responsible Down Standard (RDS), ensuring that the down and feathers come from animals that have not been subjected to an unnecessary harm. To learn more about the RDS, visit their website at:

The Helium waterproof down jacket.

Our lightest technical down jackets, in the all-new Helium Down Collection, combine 800 fill down with Pertex Diamond Fuse durability for exceptional weather protection. The Helium Down Hooded Jacket also uses an exclusive waterproof version of Pertex® Shield with Diamond Fuse fabric on hood and shoulders for added weather invincibility.

The updated, award-winning men's and women's Transcendent Down Hoodies have been staples for backpackers, climbers and outdoorspeople of all stripes for years. We kept what you loved about the old Transcendent and added what you were asking for: Injected with all-natural, 650 fill power responsibly sourced down, the new Transcendent uses wider quilting and a rebalanced, compressible down fill, allowing for faster lofting when the temperature starts to drop in camp. (If hoods aren’t your thing, the Transcendent Down Jacket offers the same warmth and feature set in a hood-free package. And this year we're introducing the Transcendent Down Pullover, for a fun twist.)

The Baja Down Hoodie jacket.

The 800 fill power Men’s and Women's Super Alpine Down Hooded Jacket are loaded with the durability, weather resistance and warmth to withstand howling wind and biting cold found at altitude—but they stow away snugly in your pack when not needed. Pertex® Quantum Pro fabric adds durability on the shoulders, sleeves and hood, and the baffled construction eliminates the cold spots that are notoriously common with other fully-quilted jackets. The Super Alpine Down Hooded Jackets are our very warmest techical down jackets.

Click here to learn more about men’s down-insulated jackets and women’s down-insulated jackets by Outdoor Research.


Shop Entire Down Collection.

Photos by Forest Woodward.