While not everyone is a technical mastermind, when you go shopping for a hunting jacket, you’ve probably heard the term “down fill power”. But what is it exactly? How do you measure it and how should it affect your buying decision? Today, we’ll try to explain these questions in layman’s terms as best as we can without getting too technical.

Down fill power – What It Tells You

To put it as simple as we can, down fill power measures how good a jacket or other camping article is insulated. While the term does not necessarily directly impact how warm a clothing article might be (explained below), it’s a good indicator of how much it can help you keep normal body temperature in harsh conditions, such as rain, snow, or when you’re climbing great altitudes.

A higher fill power indicates higher quality and more insulating down. What fill power doesn’t tell you, is how much down is in a particular article of clothing. This is an extremely important piece to understanding true warmth.

How is Down Fill Power Measured?

Regular folks have no reason to do this, but we thought it would be an interesting fact for you to know, as it will net you an even better understanding of how down works. Manufacturers place one ounce of down in a cylinder and then put a weighted disk on top of the material. After one minute, they measure how much the down has compressed to determine its capability.

More resilient down will compress less and provide more insulation, while lesser qualitative down compresses more and provides less insulation. In layman’s terms, 900 fill power is the best you can get, while 450 fill power only offers half the insulation.

For example, a jacket with 450 down will need twice as much down by weight as a 900 down jacket to have the same insulation. Therefore, consumers could be getting 900 fill power jackets, that have very little down, and therefore are not as warm as jackets with far more down in them.

If you found 3 separate jackets with the below specs, each jacket would have the same warmth, however the higher fill power jacket can be compressed to a smaller size.

Fill PowerDown Weight
450100 grams
60083 grams
90050 grams

Why Is Down So Appreciated?

Down is one of the best insulation materials due to the light weight, great insulation, and packability. It can compress into a small, packable shape, and it can go back up to normal when you need it. So for this purpose, it’s one of the best types of materials you can pack on a camping trip to ensure that you stay warm. Even if you’re already taking with you a nice tent, or some spacious hunting blinds for warmth, having a quality down jacket, vest, or bag can help you stay safer, more comfortable, and warm.

Down has featherlike plumage with numerous small air spaces in between. These air spaces capture heat and expand the material, making it insulate your body much better than any other regular jacket or camping gear could ever do.

Just How Compact Does Down Get?

As with all things, the higher the capability of the down, the higher the price. Jackets and camping equipment made from premium quality down will take a big bite out of your budget, but they are also very light and extremely easy to pack. Lesser quality down jackets and equipment won’t be nearly as packable and lightweight.

At the end of the day, it’s up to you to figure out what’s more important in your trip. Even if your jacket only has 450 down fill power, it will still protect you way better than jackets made from other materials. It’s just that it will be much bulkier. Be sure to check out our winter hiking clothing guide for more information.

Fill Weight And Why It Is Important to Search For This Particular Specification

Let’s say a 900 down fill power jacket only has 50 grams of down. Now imagine a jacket with only half the down fill power but 100 grams of down insulation. Both of them would be just as warm. However, the higher down fill power jacket will compress better.

Unfortunately, it’s highly unlikely that fill weight will be a specification that is mentioned on any website you visit. Manufacturers tend to forgo this feature and thus it becomes quite hard telling how warm a jacket will actually be. If more manufacturers would start including this in their spec sheet, measuring the warmth provided by the jacket would also become much easier.

How Should You Actually Measure Warmth?

The sad truth is that the temperature rating on a jacket can be quite misleading. There are way too many factors to take into account when it comes to how warm a jacket will keep you. Each person’s metabolism differs immensely. Some are more prone to getting cold while others can go out in a regular jacket even on the coldest winter nights.

Not only that, but the jacket’s shell material also plays a huge role. And your clothing layers also matter immensely. The only true warmth test is to actually wear the jacket in harsh conditions and see for yourself how well you can tackle the elements with that specific model.

Sleeping Bags Have Ratings You Can Trust

Unlike jackets, government regulations tackle the sleeping bag warmth issue much better. Much like the EPA measures gas mileage or the FDA measures how much permitted chemicals are in certain foods, government regulators also measure the specs of a bag to provide an accurate reading of the warmth it provides.

Of course, at the end of the day, your metabolism and other factors also contribute to this deal, but you can rest assured that if an EN-rated bag is, let’s say 10, it will be far warmer than a 5-rated sleeping bag.

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