The importance of the "Fill Power" of your sleeping bag
![Mathieu Jourjon on the Pacific Crest Trail with ultralight equipment made in Quebec and Canada. He uses an ultralight tent, backpack and sleeping bag for the long hikes. Fill power, feather quality and scientific measurement in Mount Trail sleeping bags and quilts.](https://ucarecdn.com/e5a720b8-2f93-4ce7-b694-7382c5c8dc9c/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-down-sac-de-couchage-quilt-ultraleger-plein-air-camping-longue-randonn%C3%A9e.jpg)
The fill power is the most important criterion to take into account when choosing your sleeping bag. It represents the insulation value, compression and quality of your down. The higher the fill power, the higher the quality of the down. This ensures you get through the colder nights warm. ❄
In more technical terms, fill power is the scientific measure of a feather's ability to trap air. This volume of air insulates the heat from your sleeping bag. This layer of air separates the cold air on the outside from the warm air inside the sleeping bag.
The temperature to weight ratio of sleeping bags
Every hiker is looking to maximize their warmth, while minimizing the weight of their sleeping bag. Down quality accounts for 90% of the possible weight reduction of a sleeping bag 🙂
That's why it's important to understand the value of fill power and compare it when buying a sleeping bag.
It's simple, the higher the fill power, the higher the temperature to weight ratio.
Here is an example:
![Fill power in the sleeping bag or quilt. Table that describes the differences between fill power and weight.](https://ucarecdn.com/6a032b01-9211-4381-a11f-9b3b96648616/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-sac-couchage-sleeping-bag-ultralight-ultraleger-camping-montagne-trail-quilt.png)
The compression to weight ratio of sleeping bags
As hikers, we also want our sleeping bag to take up as little space as possible in our backpack.
The higher the fill power, the greater the compression of the feather. In other words, a high fill power will ensure that your sleeping bag will take up less space in your hiking bag.
Here is an example:
![Fill power in the sleeping bag or quilt. Table that describes the differences between the weight and compression of the sleeping bag.](https://ucarecdn.com/7e97f7e2-fb92-4a02-9b43-3a68b3f989ac/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-sac-couchage-sleeping-bag-ultralight-ultraleger-camping-montagne-trail.png)
The price
The price of your sleeping bag is directly related to the value of your fill power. The higher the fill power, the higher the price of the feather.
Down sleeping bag prices can vary from $100 to $650 for the same temperature.
When you look at the product data sheet, you will see significant differences in weight, fill power and compression volume.
Example of a regular 3 seasons sleeping bag -4°C / 10°F
![Fill power in the sleeping bag or quilt. Table that describes the differences between the price and quality of down.](https://ucarecdn.com/b4d3f12a-5bf8-4a51-b6b6-dfe8b5c45a08/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-sac-couchage-sleeping-bag-ultralight-ultraleger-camping-montagne-trail-backpack.png)
Down treatment
To increase moisture resistance, many companies treat their down. This water repellent (water resistant) treatment allows for less impact of moisture on your feather 🙂
The outdoor industry
As hikers, we also want our sleeping bag to take up as little space as possible in our backpack.
The higher the fill power, the greater the compression of the feather. In other words, a high fill power will ensure that your sleeping bag will take up less space in your hiking bag.
Here is an example:
![Fill power in the sleeping bag or quilt. Table that describes the differences between fill power, outdoor companies and down quality.](https://ucarecdn.com/c57de257-0f34-44db-84e7-dfc0640a49e1/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-sac-couchage-sleeping-bag-ultralight-ultraleger-camping-montagne-quilt.png)
Can we rely on the temperature value?
Yes and No. 😝
Low quality companies
The temperatures of these companies should not be trusted at all. Their goal is to sell at low prices with poor quality.
These sleeping bags are good for sleeping in a heated cabin, but not for hiking. You have to be very careful!
Large companies
You can rely on the temperature values.
Specialized companies
You can rely on the temperature values.
Unlike large companies, specialized companies each have their own internal policy. There are some differences between specialized companies and large companies.
Politicians tend towards a normalization of these values. You can trust them!
The European standard ISO 23537
There is a European norm ISO 23537 to standardize the temperature of sleeping bags. Today, this standard is not used much in the industry. We will watch its evolution!
→ We recommend comparing two sleeping bags yourself to make sure you make the right choice.
How to compare two sleeping bags?
In order to compare two sleeping bags, the following ratio must be compared:
👉 Key ratio = Feather weight / Total area.
This ratio will allow you to calculate the number of oz / sqyd or gr / sqyd. Each company uses a different ratio according to its standards.
Note that you need to compare two sleeping bags with the same fill power. In order to know the surface area of the sleeping bag, you can use approximations from the shape of the sleeping bag 🙂
CONCLUSION
The fill power or fill factor is the most important criteria when choosing your sleeping bag. Many hikers buy sleeping bags without understanding this value 🙂
The quality of the feather has an impact on the weight, compression and price of your sleeping bag. It is important to study the issue in order to make the right choice for you.
In order to compare two sleeping bags, you need to look at this factor as well as the down weight on the product sheet.
![Fill power in the sleeping bag or quilt. Table that describes the differences between the price and quality of down.](https://ucarecdn.com/48ccef76-3aa4-4116-81d9-5a9e91330577/-/format/auto/-/preview/120x120/-/quality/lighter/fill-power-sac-couchage-sleeping-bag-ultralight-ultraleger-camping-montagne-quilt-backpack.png)
OUR RECOMMENDATIONS
Mathieu Jourjon
Founder of Mount Trail