Best Down Jackets: Arc’teryx takes the upper hand

Raw Name	Arc'teryx Alpha	Arc'teryx Cerium SV	Arc'teryx Alpha Lightweight	Arc'teryx Thorium	Patagonia Fitz Roy	Patagonia Down Sweater	Arc'teryx Cerium
Name	Arc'teryx Alpha (Men's - Women's)	Arc'teryx Cerium SV (Men's)	Arc'teryx Alpha Lightweight (Men's)	Arc'teryx Thorium (Men's - Women's)	Patagonia Fitz Roy (Men's - Women's)	Patagonia Down Sweater (Men's - Women's)	Arc'teryx Cerium (Men's - Women's)
Image
Temp (°F / °C)	-18/-28	0/-18	3/-16	7/-14	8/-13	23/-5	26/-3
Breathability	8/10	5/10	Testing	6/10	Testing	Testing	Testing
Weather Resistance	10/10	9/10	Testing	8/10	Testing	Testing	Testing
Durability	10/10	9/10	Testing	8/10	Testing	Testing	Testing
Packability	7/10	3/10	Testing	8/10	Testing	Testing	Testing
Best pick for	Warmest Arc'teryx jacket.
Review	Review	Review		Review		Review
Pit venting?	No	No	No	No	No	No	No
Stuffs into itself?	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Two way zipper?	Yes	No	Yes	Yes	No	No	No
Size Chart	[Women's]	[Men's / Women's]		[Men's]	[Men's / Women's]	[Men's / Women's]
Type	Down	Down	Down	Down	Down	Down	Down
Fill Power	850	850	850	750	800	800	850
Fill Weight (grams)	296	162	117	140	128	150	113
FP x FW	251,600	137,700	99,450	105,000	102,400	120,000	96,050
Synthetic Insulator (SI)	Coreloft	Coreloft	Coreloft Compact	Coreloft	N/A	N/A	Coreloft
SI Amount	90 g/m²	80 + 140 g/m²	40 g/m²	80 + 140 g/m²	N/A	N/A	80 + 100 g/m²
Face Fabric	N30r 2L GoreTex Infinium	Arato 7 & 10	Hadron 2L Gore-Tex Infinium	Arato 30	20D Nylon	1.4 oz 20x30D polyester	Arato 15
Activity	Climbing	All Round	Climbing	All Round	All Round	All Round	All Round
Fit	Regular	Regular	Regular	Regular	Regular	Regular	Trim
Weight	805 g / 1 lb 12.4 oz	415 g / 14.6 oz	540 g / 1 lb 3 oz	517 g / 1 lb 2.2 oz	632 g / 1lb 6.3 oz	428 g / 15.1 oz	335 g / 11.8 oz
Length (CB)	86 cm / 34 in	69.5 cm / 27.4 in	?	71.5 cm / 28.1 in	74 cm / 29 in	67 cm / 26.25 in	?
arc-mens-url	https://www.arcteryx.com/us/en/shop/mens/alpha-parka	https://arcteryx.com/us/en/shop/mens/cerium-sv-hoody	https://www.arcteryx.com/us/en/shop/mens/alpha-lightweight-parka	https://arcteryx.com/us/en/shop/mens/thorium-hoody			https://arcteryx.com/us/en/shop/mens/cerium-hoody
arc-womens-url	https://www.arcteryx.com/us/en/shop/womens/alpha-parka			https://arcteryx.com/us/en/shop/womens/thorium-hoody			https://arcteryx.com/us/en/shop/womens/cerium-hoody
pat-mens-url					https://www.patagonia.com/product/mens-fitz-roy-down-hoody/85500.html	https://www.patagonia.com/product/mens-down-sweater-hoody/84702.html
pat-womens-url					https://www.patagonia.com/product/womens-fitz-roy-down-hoody/85505.html	https://www.patagonia.com/product/womens-down-sweater-hoody/84712.html
rei-mens-url		https://www.rei.com/product/873043		https://www.rei.com/product/209333/arcteryx-thorium-down-hoodie-mens	https://www.rei.com/product/175229	https://www.rei.com/product/208592
rei-womens-url	https://www.rei.com/product/191824/arcteryx-alpha-insulated-parka-womens	https://www.rei.com/product/105020			https://www.rei.com/product/174864	https://www.rei.com/product/208408
backcountry-mens-url					https://www.backcountry.com/patagonia-fitz-roy-hooded-down-jacket-mens	https://www.backcountry.com/patagonia-down-sweater-mens
backcountry-womens-url					https://www.backcountry.com/patagonia-fitz-roy-down-hooded-jacket-womens	https://www.backcountry.com/patagonia-down-sweater-womens
amazon-mens-url		https://www.amazon.com/Arcteryx-Cerium-SV-Down-Jacket/dp/B00GV4IDJE			https://www.amazon.com/Patagonia-Fitz-Parka-Large-Underwater/dp/B00OZG9ZKQ	https://www.amazon.com/Patagonia-Down-Sweater-Jacket-Mens/dp/B001NAC5V8
amazon-womens-url		https://www.amazon.com/Arcteryx-Cerium-SV-Hoody-Sapphire/dp/B01N8ZRDDR				https://www.amazon.com/Patagonia-Down-Sweater-Womens-Violetti/dp/B00GR9H3FI
image-url	https://images.arcteryx.com/F22/1350x1710/Alpha-Parka-Dynasty.jpg	https://images.arcteryx.com/F22/1350x1710/Cerium-SV-Hoody-Phenom.jpg	https://images.arcteryx.com/F22/1350x1710/Alpha-Lightweight-Parka-Black.jpg	https://images.arcteryx.com/F22/1350x1710/Thorium-Hoody-Forage.jpg	https://www.patagonia.com/dw/image/v2/BDJB_PRD/on/demandware.static/-/Sites-patagonia-master/default/dw2c6611cb/images/hi-res/85500_APBL.jpg?sw=1914&sh=1914&sfrm=png&q=95&bgcolor=f5f5f5	https://www.patagonia.com/dw/image/v2/BDJB_PRD/on/demandware.static/-/Sites-patagonia-master/default/dw42739c12/images/hi-res/84702_FGE.jpg?sw=1914&sh=1914&sfrm=png&q=95&bgcolor=f5f5f5	https://images.arcteryx.com/F22/1350x1710/Cerium-Hoody-Habitat.jpg

First thing you should know about down jackets is that you should only consider getting one for stationary use, in dry weather. 

Because, all down jackets offer: 

• Low breathability, 
• Poor wet weather performance, 
• Fragile outer shell.

Always. 

No exceptions. 

If this isn't you, then you should stop reading this post and go check out my Best Synthetic Insulated Jackets article. 

I'd also recommend you to check out my Best Arc'teryx Jackets and Best Patagonia Jackets articles. 

#Important note: A down jacket will lose its insulating capability under fairly wet conditions. Either from your sweat or wet weather. 

That's why, if you're going to be using them in damp areas, I'd urge you to consider getting a synthetic insulated jacket instead. They're mostly heavier, but perform better in wet conditions. 

Temperature Ratings

The warmth data provided below for each product are obtained either by: 

• Trying them out, 
• Analyzing them scientifically,
• And/or gathering tens of authentic, non-biased offline user experience.

As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. 

Let's clarify the reasons behind this. 

Warmth

Warmth is the most important thing you should focus on when getting a down jacket. There are two major factors to it: 

• Fill power, 
• Fill weight.

Note that these are major two factors, not only two factors. 

Fill Power

The word "down" is typically mostly referred to as "fill" in down insulated garment language. 

Fill Power refers to the fully expanded end volume of a 1 oz down (goose or duck). It's in cubic inches. 

For example, a 800 FP (fill power) down will end up getting as large as 800 cubic inches when it's fully expanded at rest. 

By the way... 

Fill power isn't only about warmth level at all. Having said that, all I'm currently trying to accomplish is to decode the nature of warmth in an analytical way. 

This is why I'm going to skip other roles of fill power and will get back to it later in this post. 

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

Moving on to our other major factor... 

Fill Weight

Fill weight is the amount of down the insulated piece is equipped with. It's just as important as fill power when it comes to warmth.  

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

That said, the role of fill power on other factors (long term warmth, warmth during movement, warmth distribution, compressibility) is significantly greater than fill weight. 

Important: Warmth Calculation

Reminder: Fill power and fill weight are the two most important factors when it comes to warmth. 

On a larger scale, assuming both jackets are equipped with identical synthetic insulation (or none of it), it is possible to make very close estimations by multiplying them when comparing warmth ratings of two different pieces. 

For example...

• Rab Neutrino Pro offers 227 grams of 800 FP down.
  • 227*800 = 181,600
• Outdoor Research Alpine Down offers 182 grams of 800 FP down. 
  • 182*800 = 145,600

Since 181,600 is significantly greater than 145,600; it's safe to say that the former will be warmer than the latter. 

Now...

There are reasons why this mostly won't work on a smaller (or sometimes even on a large) scale. 

The main reasons include but are not limited to: 

• Presence of other synthetic insulators,
• Length,
• Bagginess,
• Outer fabric,
• Fill power (I know this is confusing... ignore it for now).

Let's clarify them briefly. 

Synthetic Reinforcements

This is one of the primary reasons for this. For example, Arc'teryx always uses synthetic insulation strategically in high wear areas for all their down jackets. 

As you can guess, this is part of the reason why they're listed warmer than down jackets with equal FP * FW values. 

Length

In colder weather, it becomes much harder to keep your legs and feet warm than your torso and arms. 

This is why, the longer the hem length, the warmer the jacket will feel. And the difference is pretty noticeable. 

Bagginess

I talked about this more in detail in 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. 

Weather Resistance & 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 well weather resistance since they get clumped and loses their loft when they get wet. 

This is the case regardless from getting wet through your sweat or weather conditions. 

That being said, it's still possible to sort them by their strength. But the difference is minimal here - so much that it might not even be noticeable: 

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

Other impacts of Fill Power

Higher FP will retain its loft with minimal loss during movement. Whereas a lower quality (which is a lower FP) down will do a poor job with this. 

For the sake of simplicity and trying not to make this a scientific article, I decided to place equal importance (weight) on fill power and fill weight when calculating FP * FW values. 

But, in reality, I'd actually place more weight on fill power. Maybe squaring the FP and then multiplying it with FW would be a more accurate calculation to yield better results. 

How do down jackets compare to synthetic jackets?

Here's the full data set for Arc'teryx's and Patagonia's almost all insulated garments. 

Lastly, if you're interested in Patagonia only, check out my Best Patagonia Down Jackets post.