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How much fill for a down jacket?

When shopping for down jackets, one of the most important factors to consider is down fill. Getting to grips with the amount of fill you need for your jacket will help you ensure your jacket provides the warmth and comfort you need. Down fill affects every aspect of your jacket's performance, from weight to warmth and insulation. In this guide, we’ll explain everything you need to know about fill power, from what it is to how much you might need.

What is down fill power?

If you’ve ever noticed three numbers printed on your down jacket, this indicates its fill power. Fill power measures the loft or fluffiness of down and its effectiveness at trapping warm air. Under laboratory testing, the down is compressed and then tested to see how much space one ounce of down takes up in cubic inches. The fill power is then given a rating which typically ranges from 400 to around 900. A higher fill power means the jacket has a high warmth-to-weight ratio – exceptionally warm but weighs less. Jackets with a higher fill power indicate a high quality of down and are often used in technical and extremely cold jackets.

There is also fill weight. This refers to the actual quantity of down that’s been used to fill your jacket in ounces or grams. If a down jacket has a higher fill power with a low fill weight, it’s likely lightweight and easy to compress. However, it may not be as warm as a jacket with more down fill. On the other hand, a jacket with a heavier down fill weight will offer greater warmth, but may be heavier.

What are the different types of down?

Depending on the different brands, duck and goose down are commonly used in these insulated jackets. Goose down, which is what we use in all our down clothing, is considered superior due to its larger clusters. After all, geese are bigger than ducks. Duck down is still effective at insulating and is often less expensive. Goose down jackets are generally better suited for very cold conditions, while duck is better for milder temperatures.

All the goose down we use in our jackets is certified by the Responsible Down Standard or RDS. This is a voluntary code that demonstrates our commitment to the welfare of birds. At every stage of the supply change, the well-being of the birds is monitored, with no live plucking or force-feeding permitted.

How much fill do you need?

In most cases, the amount of down fill you need in a jacket will largely depend on what you intend to use the jacket for and the temperature you’ll be wearing it in.

  • Mild conditions: if you’ll be wearing your jacket in fairly cool, mild conditions a fill power of between 500 and 600 and a fill weight of around 100 to 150 grams should be sufficient. This will give you warmth but without too much additional weight. These types of jackets are ideal for taking with you ‘just in case’. As it is lightweight, you can easily compress it into a stuff bag or your backpack.

  • Moderate winter conditions: when temperatures are at or just under freezing, a jacket with a fill power of 600 to 700 and a fill weight of around 150 to 250 grams is ideal. This warmth/weight ratio provides good insulation without adding weight. You may also want to consider what features you need for this type of climate, such as water-resistant outer shells and adjustable hoods.

  • Extremely cold: when faced with the coldest temperatures, you need a higher fill power of around 700 or 800 and a fill weight of at least 250 grams. This should provide you with the optimal warmth you need while also remaining lightweight.

When looking to buy a new down jacket, understanding the ins and outs of down fill power and weight will help you make an informed choice. Once you've got to grips with how it works, you can ensure that you will choose the best down jacket for your specific needs.