Temperature Ratings of Jackets (Quick cheatsheet)

Summary

Most outdoor apparel companies say that providing temperature ratings for their jackets isn't possible.

And to be fair, they're not incorrect. There are tons of fluid parameters that are difficult, if not impossible, to measure. And let's not forget the very subjective nature of the feeling of "warmth." 

Having said that ... it is possible to provide approximate jacket temperature ratings for an average person if we make some strict assumptions around layering and weather conditions. Which is exactly what you'll find in this post. 

Before we dive deep, here's our detailed list of temperature ratings of insulated jackets from brands like Arc'teryx, Patagonia, and RAB. 

Table of contents

The context of this study will be evaluated in two parts: 

• Working principles of down jackets 
• Working principles of synthetic insulated jackets 

Let's get to it. 

Understanding the Working Principle of Down Insulated Jackets

Down quality and down amount are the two most important factors when it comes to the ultimate warmth provided by any down insulated garment. 

You'll mostly come across these factors as fill power and fill weight, respectively. The word "down" is typically referred to as "fill" within the context of articles of down clothing or gear (think sleeping bags). 

Let's take a look at fill power first. 

Fill Power

Fill power represents the fully expanded volume of a 1 oz down (goose or duck). It's measured in cubic inches. 

For example, 800 FP (fill power) down will take up 800 cubic inches when it's fully expanded. 

The fill power number varies anywhere from 500 to 1000, although the majority of quality brands (such as Arc'teryx, Patagonia, Feathered Friends, Outdoor Research, Marmot, REI Co-op, Enlightened Equipment, Rab, Black Diamond, Mountain Equipment and Mountain Hardware) typically use down between 650 FP and 850 FP. 

As you'll see, there are outliers, though. A notable one would be Feathered Friends Eos, which is equipped with a whooping 900 FP down. 

Speaking of fill power, warmth isn't the only thing it affects. 

Other roles of fill power

It has three other important roles: 

• Loft retention during movement: Higher FP down will retain its loft with minimal loss during movement. The lower the FP, the larger the loss in this department. 
• Higher impact on end warmth: Compared to FW (fill weight), FP has a larger impact on the warmth an insulated jacket provides. 

• Durability of insulation capability 
  • A jacket with a higher FP down minimizes its loss of insulating power over time. You'd be able to use a 850 FP down jacket for decades, and it'll feel almost as warm as the first day you put it on. 
  • A jacket with a lower FP down, on the other hand, might not prove as durable. In our experiences, jackets equipped with 650 FP down are more likely to feel noticeably colder after, say, 2 or 3 years. 

• Compressibility: A jacket with a higher FP down will offer a smaller packed size. 

Here's a video also does a good job explaining fill power: 

Moving on to our other major factor... 

Fill Weight

Fill weight is the total amount of down the jacket is equipped with. 

Some other resources might claim that fill weight is much less important than fill power when it comes to warmth, but that's far from reality.

In terms of warmth, fill weight is very, very important. Almost (in some conditions it even is) just as important as fill power. 

Because, just like fill power, fill weight also directly affects the total amount of air trapped within the vacant spaces of down. 

Warmth Calculation

As explained earlier, fill power and fill weight are the two most important factors when it comes to warmth. 

In many cases, on a larger scale, assuming both jackets are equipped with the same amount of equally capable synthetic insulation, it is possible to make very close estimations by multiplying them when comparing warmth ratings of two different pieces. 

For example...

• The Arc'teryx Cerium SV offers 162 grams of 850 FP down. 
  • 105*900 = 137,700
• The Rab Positron Pro offers 300 grams of 800 FP down. 
  • 116*650 = 240,000

Because 240,000 is significantly greater than 137,700, it's safe to say that the Rab Positron Pro will be noticeably warmer than the Arc'teryx Cerium SV. 

One point should be made in here is that although the Positron will be warmer, the higher fill power down of the Cerium SV means the Arc'teryx jacket will:  

• stay almost equally warm even after decades 
• won't lose its insulation during movement
• will be more compressible/packable 

Now ... 

There are reasons why this mostly won't work on a smaller scale (more on these later, under Other Factors heading). 

Understanding the Working Principle of Synthetic Insulated Jackets

Synthetic insulated jackets imitate the working principle of down insulated jackets. They're equipped with artificial insulators rather than natural down obtained from geese and ducks. Some examples of these artificial insulators are Coreloft and PlumaFill.

However, comparing the temperature ratings of synthetic insulated jackets is more difficult because, unlike fill power in down jackets, there isn't a common denominator to compare different types of synthetic insulators in an analytical way. 

What do CLO values represent? 

CLO value is the insulation power of an insulation setting.

For example, this value is 0.92 for 1 ounce (28.35 grams) of a dry PrimaLoft One for one square yard. The important thing here is that unlike fill power, CLO is not a characteristic that is unique to one ounce of the material.

As you see in the example above, it isn't independent from the area of insulation (square yards). 

So, a higher CLO actually points to the insulation capability of an insulation setting as a whole. It does NOT necessarily mean that the insulator being used is any more capable than an insulation setting put together with a weaker insulator. 

Given the right amount of thickness, any insulator can achieve desired CLO value. It's just going to end up being heavier. So, metaphorically, you can think of CLO value in synthetic insulated jackets as similar to the FP * FW value in down insulated jackets. 

• Read more about CLO values: https://outdoorcrunch.com/clo-values/ 

Unfortunately, obtaining the CLO value for commercial products is absolutely impossible. Having said that, we can (and we do) use a made-up parameter to CLO/oz/yd² to replicate FP in down jackets. 

But unfortunately, a new problem arises here. A fair amount of manufacturers come up with their unique insulators - such as Coreloft, PlumaFill, Octa, Stratus, FullRange, etc. 

And just like CLO values, they're unwilling to reveal the CLO/oz/yd² values of their insulators, which are the numbers we would need to determine the warmth. 

I asked Arc'teryx and Patagonia about this, and came back empty handed. But, during my research, I did come across some useful information that we can leverage. For example, as it turns out, the CLO/oz/yd² value for PrimaLoft One is 0.92. The value is 0.79 for PrimaLoft Sport and 0.74 for PrimaLoft Eco. 

However, these values aren't certain or completely trustworthy by any means. They aren't the results of scientific studies. I didn't detect them in any other place rather than forums, Reddit, or contacting manufacturers myself. 

In the end, I put what I could find together and did my best to make an estimation. Fortunately, this calculation using the numerical value CLO was not the only information I had in my hands. 

I had two additional (at least equally helpful) data: trying them out myself when I could, and gathering offline user experience. 

Warmth Evaluation

So, in the end I used at least two of these three factors to estimate the overall temperature rating of an insulated jacket: 

• Analyzed them scientifically (as explained earlier) 
• Tried them out myself when I could
• And/or gathered offline user experience. 

And mostly all three above. 

In addition to insulation types and amounts (which is what I covered so far), there are also other factors that impact the warmth of an insulated jacket. 

Other factors

Let's talk about the most important and most common examples of these factors.

In most cases, these are considered minor next to insulation-specific qualities. But they do have a noticeable effect, and combined together, they might come close to affect the warmth as much as the insulator capability and amount. 

• Bagginess
• Length
• Outer (face) fabric
• Distribution of insulation 

Bagginess

I also talked about this more in my my Arc'teryx Thorsen vs Therme vs Camosun post. 

Briefly, the amount of trapped air increases as the jacket gets baggier. So more air works as insulation, and ultimately you're kept warmer. 

There certainly is something as "too baggy," though. After some point, more inner volume only holds the warmth back. 

Length

This has two effects. The first is the amount of trapped air against your body, which is explained above.

And second, in colder weather, it becomes much harder to warm your legs and feet than your torso and arms. 

This is why a jacket with a longer hem length, such as a parka, will feel warmer. And the difference is pretty noticeable. 

Outer fabric 

Outer fabric is actually much more about weather resistance, but it also affects warmth a little bit. 

As explained earlier, no down jacket is able to offer top notch weather resistance because down clumps and loses its loft when wet. It doesn't matter if that moisture comes from your seat or from weather conditions.  

Having said that, it's still possible to prevent it to a certain degree. Some products offer a more fragile face fabric, while others can bead water more efficiently. These are directly proportional to face quality and DWR coating. 

For face fabrics, I'd list them like this: 

Perfex Quantum Pro = Arato 30 > Perfex Quantum > Arato 10 = Drilite Loft 40D > Arato 7 = Drilite Loft 20D > others.

For synthetic jackets, outer fabric affects the warmth noticeably less. Why? Because the benefit of synthetic insulation is it doesn't lose its insulating properties when wet. 

Fill distribution

Some products of my favorite brand Arc'teryx are guilty of this. Take the Firebee AR (read my review), for example. Nothing is wrong with the insulation at the back, collar and torso. They feel perfectly warm. 

Whereas the insulation in the arms, especially in the lower arms, is slightly inadequate, which in the end affects the warmth of the jacket. 

Reinforcements

Some (most?) down jackets are reinforced with synthetic insulation in strategic locations. More often than not, these are high-wear areas such as shoulders, back, elbows, etc.

For the sake of simplicity, I don't list them in my tables - although I do take them into consideration when evaluating the end warmth of a jacket. 

This is why you may see a jacket with a smaller FP x FW rating outscoring a jacket with a higher FP x FW rating - the former is equipped with (more) synthetic insulation reinforcements. 

Results: Temperature Ratings

Down jackets lose insulating power noticeably when in contact with water. Synthetic jackets don't. This is why the dry weather assumption was made for both of them. 

Fill Values of Insulated Jackets

Updated for Winter 2024. 

• Fill weight of Arc'teryx Alpha Parka (Men's - Women's) is 296 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 8875 cubic inches of down fill volume. It's also reinforced with 90 g/m² of Coreloft.  
• Fill weight of Arc'teryx Alpha Lightweight (Men's - Women's) is 117 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3508 cubic inches of down fill volume. It's also reinforced with 40 g/m² of Coreloft Compact.  
• Arc'teryx Atom (aka LT) ( Men's - Women's) is equipped with 60 g/m² of Coreloft Continuous.
• Arc'teryx Atom SV (Men's - Women's) is equipped with 120 g/m2 of Coreloft Continuous.
• Arc'teryx Atom SL (Lightweight) (Men's - Women's) is equipped with 40 g/m² of Coreloft Compact.
• Fill weight of Arc'teryx Beta Down Insulated (Men's - Women's) is 126 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume. It's also reinforced with 80 g/m² of Coreloft.
• Arc'teryx Beta Insulated (Men's) is equipped with 80 g/m² of Coreloft Continuous.
• Arc'teryx Beta Insulated Coat (Women's) is equipped with 80 g/m² + 120 g/m² of Coreloft .
• Fill weight of Arc'teryx Cerium (aka LT) (Men's - Women's) is 113 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3388 cubic inches of down fill volume. It's also reinforced with 80 + 100 g/m² of Coreloft.
• #REF!
• Arc'teryx Cerium Hybrid (Women's) is equipped with 98 g/m² of Coreloft.
• Fill weight of Arc'teryx Liatris (Women's) is 93 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 2788 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
• Fill weight of Arc'teryx Liatris Parka (Women's) is 136 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 4078 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
• Arc'teryx Nuclei (aka FL) ( Men's - Women's) is equipped with 65 g/m² of Coreloft Continuous.
• Arc'teryx Nuclei SV (Women's) is equipped with 190 g/m2 + 90 g/m2 of Coreloft Continuous.
• Fill weight of Arc'teryx Patera (Women's) is 67 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 1773 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
• Fill weight of Arc'teryx Patera Long (Women's) is 204 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5397 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
• Arc'teryx Proton SL (Lightweight) (Men's - Women's) is equipped with 94 g/m² of Octa Loft.
• Fill weight of Arc'teryx Therme Parka (Men's) is 120 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3175 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
• Fill weight of Arc'teryx Therme SV (Men's) is 211 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5582 cubic inches of down fill volume. It's also reinforced with 60 g/m² of Coreloft.
• Fill weight of Arc'teryx Thorium ( Men's - Women's) is 140 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3704 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
• Fill weight of Arc'teryx Thorium Parka (Women's) is 209 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5529 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
• Fill weight of Arc'teryx Thorium SV (Men's) is 169 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 4471 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
• Fill weight of Arc'teryx Thorium SV Parka (Men's) is 195 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5159 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
• Fill weight of Black Diamond Access Down (Men's - Women's) is 112 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 3161 cubic inches of down fill volume.
• Fill weight of Feathered Friends Eos(Men's - Women's) is 105 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 3333 cubic inches of down fill volume.
• Fill weight of Feathered Friends Khumbu (Men's) is 378 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 12000 cubic inches of down fill volume. It's also reinforced with 200 g/m² of Primaloft Gold.
• Fill weight of Patagonia AlpLoft (Men's) is 295 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8325 cubic inches of down fill volume.
• Patagonia DAS (Men's - Women's) is equipped with 133 + 40 g/m² of PrimaLoft Gold Insulation Eco.
• Patagonia DAS Light(Men's) is equipped with 65 g of PlumaFill.
• Fill weight of Patagonia Down Sweater (Men's - Women's) is 150 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 4233 cubic inches of down fill volume.
• Fill weight of Patagonia Downdrift (Men's - Women's) is 279 grams. Its fill power is 600 cubic inches per ounce, which equals to a total of 5905 cubic inches of down fill volume.
• Fill weight of Patagonia Fitz Roy (Men's - Women's) is 128 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 3612 cubic inches of down fill volume.
• Patagonia Isthmus (Men's) is equipped with 60 g/m² of ThermoGreen.
• Fill weight of Patagonia Jackson Glacier (Men's - Women's) is 141 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3482 cubic inches of down fill volume.
• Fill weight of Patagonia Jackson Glacier Parks ( Women's) is 218 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 5383 cubic inches of down fill volume.
• Patagonia Micro Puff (Men's - Women's) is equipped with 65 g/m² of PlumaFill.
• Patagonia Nano Air (Men's - Women's) is equipped with 60 g/m² of FullRange.
• #REF!
• Patagonia Nano Puff (Men's - Women's) is equipped with 60 g/m² of PrimaLoft Gold Insulation Eco.
• Fill weight of Patagonia Silent Down (Men's - Women's) is 109 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2691 cubic inches of down fill volume.
• Fill weight of Patagonia Stormshadow (Men's) is 259 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 6395 cubic inches of down fill volume.
• Fill weight of Patagonia Tres 3-in-1(Men's - Women's) is 118 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2914 cubic inches of down fill volume.
• Fill weight of Rab Electron Pro (Men's - Women's) is 180 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5079 cubic inches of down fill volume.
• Fill weight of Rab Microlight Alpine (Men's - Women's) is 153 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume.

CLO Values 

Find CLO values of synthetic insulators in this table. 

• Fit

Canberk is 5'11" and 165 pounds, with an athletic build. Size Medium fits him perfectly across almost all brands and product lines. 

• Arc'teryx's 2024 men's fit revision

Here's what Arc'teryx says about its most recent fit revision: 

Source: https://arcteryx.com/us/en/help/sizing/mens/tops/new

Not all jackets come with the revised fit - only the ones with following statement: 

Sources: Richard Nisley's "A Revised Paradigm for Understanding Garment Comfort Limits" paper, Hohenstein Institute's Primaloft Thermal Performance paper and Primaloft's own fact sheets (Gold Eco, Silver, Black).