Which size compression bag?

[Jason Click]

I bought a new sleeping bag. Here's the link:
https://www.sierradesigns.com/p-338-verde-40.aspx

It didn't come with a compression sack so I'm looking to get one. My question is the stuff size dimensions. Is that the dimensions for the sleeping back at it's smallest compression or is the dimensions the size bag I need to get? I of course want to compress it as small as possible to save space but I don't want to have a wrestling match every time I pack it up.

Stuffed diameter: 7" / 18 cm
Stuffed length: 17" / 43 cm

I was looking at some compression sacks on eBay. One had the following dimensions:

Dimensions: 7 x 16in (18 x 41cm); [M] 9 x 20in (23 x 51cm); [L] 11 x 23in (28 x 58cm); [XL] 12 x 26in (30 x 66cm)

ALPS Mountaineering Compression Sack

Thanks for the help!

[James Marco]

This is really variable depending on a couple things.
1) Durability : How long do you want it to last? Synthetics are not known for being "highly compressible" and "high durability" at the same time. Synthetic fills take a set, with every compression, unlike down.
A small size will last 1 year
A medium size will last 2 years
A large size will last 3-4 years
2) Diameter is not the same as width. Calculate the cicumfernce to get the distance around. D=C/Pi or 7=x/3.142. Or, about 22". Soo, a 7" wide bag(times two for two sides is 14") will clearly not fit at their recommended compression.

I would probably use the large size based on these numbers.

[Joe Clement]

I think those times are optimistic. I'd cut them in half.

[M B]

You dont need or want to compress your bag. You want to lightly stuff it.

Compression sacks are usually heavy, several oz, and can ruin the bag eventually.

In a UL pack , the sleeping bag can provide shape and support for the pack bottom and a solid base to pack other gear on top of. Over-compressing it can prevent that. 17" is too long really though to go horizontal in bottom of most UL packs. A slightly larger dia and shorter length might be necessary to fit well in a pack.

I would get a cuben drybag, with the dia needed. That way its light , waterproof.

[Pilate de Guerre]

Don't use a compression sack unless you really need the pack volume. Just put it in the bottom of your pack inside a trash compactor bag that you use as your pack's water proofing. As you put the rest of your gear on top it'll compress somewhat, but only the minimum needed. Lighter and better on the synth fill.

[Jeffs Eleven]

-1 to compression

[Eric Blumensaadt]

I have to use a large compression sack for my Mountain Hardware Polarguard 3D filled bag. It's a -20 F. bag and it's BIG.

It's big partly because of the Polarguard fill and partly because of its added expandable full length gore and zipper which all runs parallel to the main zipper. The gore opens up another 4 inches, permitting me to insert my WM Megalite down bag inside (and still maintain most of its loft) in the very unlikely chance that I'd have to brave -40 F. weather.

So, yes, sometimes, just to get a danged bag in a reasonable sized sack, a compression sack is necessary. And then it STILL won't come close to fitting in the sleeping bag compartment of my large Dana Terraplane winter pack so I have to strap it on the bottom of the pack.

That said I open the bag up and put it in the dryer when I get home to "unlax" some of the compressed synthetic fibers a bit. Then it goes in storage laid out full length under my bed. So far it seems to have kept 90% of its loft.

For summer I COULD squeeze my WM down bag into a smaller OP waterproof roll-top stuff sack but I made the decision to go with a slightly larger OP bag so I wouldn't damage the down by hard-as-a-brick stuffing. It's a trade-off. I used the largest compression bag I could find for the synthetic winter bag.

[Bob Salcedo]

I use the Sea to Summit and Exped waterproof compression sacks for a variety of reasons and have have used other brands for years. My down bag is 8 years old and as lofty and good as ever with no rips and tears from being compressed by other gear. It has fallen out of the raft and floated away only to be retrieved and bone dry, something I'm not willing to try with a plastic bag.

I'm willing to add some grams for the durability, waterproofness, and double duty (Exped as an air pump) that these provide. I have the 22 liter Exped sack (yellow) and the medium and large Sea to Summit sacks.

No I don't carry them at the same time.

Bob

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