Compression dry sack - what size?

I’m looking to buy a compression dry sack for my sleeping bag but don’t know what size to get. I’ve seen good reviews for the Sea to Summit eVent bags, which come in 15, 20 and 30 Liters (med, large and XL).

My sleeping bag is an LL Bean synthetic rectangular (non-mummy style), which packs down normally in a stuff sack about 12x18" I’m estimating. Since the S2S bags are pretty expensive, I would prefer to get the smallest bag that will do the job.

Any advice?

I think you need
to get one that is essentially the same size as your stuff sack (or at least close). That is because you have to stuff the sleeping bag into the compression sack just as you would into a normal sack before you get to use the compression straps to to compact it down.

I found I could use just a slightly smaller compression sack than my stuff sack because the stuff sacks normally have a bit of room left after stuffing. But it was not as if I could use a 10"x6" compression sack if the original stuff sack was 14"x8". In that case I might get away with 13"x8" or 14"x7" compression sack if it was the closest thing to my stuff sack size.


Thanks, that helps. The 20L size is probably closest to the stuff sack I’m using now.

I use
the Sea to Summit eVent L for a synthetic bag. I’ve also got a M I use for clothing and an XS I use for a cag. The M would be tight except for maybe the lightest/smallest of synthetic bags.

Sack size.
If I wasn’t sure I would err on the side of larger rather than smaller.

Nothing worse than trying to shove 20 liters of bag into a 15 liter sack.

big sleeping bag
That’s a big sleeping bag to try and compress into a ball that will still fit nicely in a hatch. Exped makes lengthwise waterproof compression bags that work well for bulky sleeping bags:

They compress lengthwise and I find it easier to fit long/thin into a hatch.

you’re supposed to compress it first
then it fits right in

Good point on lengthwise compression
I have one bag/compression sack combo where I have to be careful about overcompressing. If I really tighten down on the compression straps the sleeping bag starts making the sides of the compression bag stick out and I can not get it into the dry bag (Note: this compression bag is not waterproof). I have to loosen the straps just slightly and kind of pound on the sides until it is just narrow enough to slip into the dry bag. That dry bag is the largest one I can slip through my hatches. Lengthwise compression (making it narrower but same length) would allow me to use a longer narrower dry bag that would go easily through the hatch.

It is definitely something the OP should consider.


compression sack
Well I looked at the Sea to Summit dry compression bags at REI and still couldn’t decide between the M and L (15/20 liter) sizes, so I opted for the smaller one. Salesman wasn’t much help, telling me to go by the sizing chart on the box. Got home and tried to fit my sleeping bag in the sack, but it wasn’t quite big enough. The sleeping bag would fit in the sack but there wasn’t enough room left over to seal it (you are supposed to fold the top several times). So I’ll be heading back to REI tonight for the 20L bag. That’s OK because I need to pick something else anyway.

Try this
Stuff you bag in the medium event sack, then compress it before trying to do the waterproof folding seal, then, after the bag has compressed you may have enough room to adequately fold the flap three times and buckle it. Compression of a sleeping bag takes a bit of time and effort to allow all the air to release through the e-vent.---------

Forget the event…
Just use a trash compactor bag and the stock stuff sack, or two compactor bags if you’re paranoid. Much cheaper and works just as well as the event jobies…

I use 15L Outdoor Research compression drysacks for my tent and my sleeping bag. My bag is a rectangular synthetic in extra long length(Big Agnes) and it fits well.