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Understanding Down Jackets

Choosing a down jacket or any type of down product in general is one of the most important decisions when selecting mountaineering gear. A warm down jacket to use when resting on the mountain or for using around basecamp is an essential layer on any mountaineering trip.

Therefore, it is super important to know what to look for when picking the perfect down jacket for your climb. There are many factors to consider when choosing a down jacket however the two most important, and often the most misunderstood things, are fill power and fill weight:

  • Fill Power: The volume or the “loft” of a down jacket is how much space one ounce of fully expanded feathers takes up within a jacket (for example a down jacket will a fill power of 800 means that 1 once of fully expanded feathers will take up 800 cubic inches.) The loftier the down the higher ratings it has the warmer it is!
  • Fill weight: Deals directly with the weight of the down in the jacket. Heavier jackets are warmer but compact less and lighter jackers are not quite as warm but generally compress more.

Other important considerations:

Time of year/ Region:

  • The type or warmth of the down jacket depends on where you are going and the time of year. It is important to research the weather and conditions for the time of year of where you will climb. Will you climb in milder summer conditions or in cold air at high altitudes, in rain, deep snow or storms? Remember that you will also have to pack everything in a backpack, so make sure that the jacket you decide on can compact enough to fit in your pack along with your other things.


  • Down jackets are often the last layer that we recommend putting on. We consider it the “reserve layer” because we put it on mostly when stopping for a break while climbing and hanging out in base camp, rarely do you climb with a down jacket on. Therefore, we advise you to make sure you are getting a size that can fit over all your other layers and still zip up comfortably. It can sometimes be necessary to get a size up, but the best is to try on the jacket before purchasing it.
  • We also recommend buying a jacket with a hood as hoods help retain heat.


At our Guide Hut we have two down jackets that we rent for climbs in the Cascades. These two jackets provide a great starting point for finding the perfect down jacket for you and understanding the difference of the down jacket depending on the time of year and conditions.

  • For early and late season we recommend renting the Mountain Hardware Phantom Parka which has a fill power of 800 and a fill weight of 17oz. This makes it a very warm jacket but not the most compactable, making it better for colder climbs.
  • For Mid-Season we recommend the HIMALI Accelerator Down Jacket which has a fill power of 700 and a fill weight of 11 oz. It is a lighter and more compactable down jacket but not quite as warm as the Phantom Parka which is why it’s great for mid-season climbs in the Cascades.

It is super important to consider both the down fill and the down weight when choosing down products, and to understand your predicted use of the jacket, the weather, and your personal preferences, to find the perfect combination between warm and comfortable yet packable down products for your next adventure!