Choosing A Compression Sack

From backpacking and bikepacking to kayak adventures to overland motorcycle tours and snowmobiling—compression sacks are always handy when space is at a premium.

These space-saving storage bags can compress bulky soft items like sleeping bags and down jackets to almost a third of their size—making more room in your pack for precious peanut butter and chocolate. (Exactly how much reduction in volume you can expect will depend on the materials of the product you are trying to compress).

To help you get the right compression sack for your adventures, here are some questions (and answers) that will guide your choice:

WHAT SIZE COMPRESSION SACK DO I NEED FOR MY SLEEPING BAG?

Because sleeping bags vary in their packed volume—depending on whether you have a down bag or synthetic bag and what shell and liner fabrics they use—it’s not possible to simply equate a bag temperature rating with a compression sack size. Instead, you’ll need to determine your sleeping bag’s volume and equate that to liters.

HOW DO I DETERMINE THE VOLUME OF MY SLEEPING BAG?

If you’ve bought a Sea to Summit sleeping bag, you can look up the volume of the bag on our product pages. If you’re determining the volume of another bag, follow the process below:

• Put your bag in a cardboard box (one which is larger than the bag)
• Measure the length and width of the box in inches
• Press the sleeping bag down firmly until the upper surface is roughly level in the box
• Measure the average depth that the bag occupies in inches
• Now multiply length x width x depth = volume in cubic inches
• Divide the total by 61 = volume in liters
• If you use the metric system, measure in centimeters and divide the total by 1000 to calculate the volume in liters

WHAT KIND OF COMPRESSION SACK SHOULD I CHOOSE?

WATERPROOF + EXTREMELY DURABLE: EVAC COMPRESSION DRY BAG HD

WATERPROOF + LIGHTWEIGHT: EVAC COMPRESSION DRY BAG UL

Choose it if: you need compression and waterproof protection, and weight is critical.

The eVac Compression Dry Bag UL is the ultralight version of our crowd-favorite eVac Compression Dry Bag LW. Made with bluesign-approved 30D Ultra-Sil fabric, it’s 40% lighter than our original design but still retains our revolutionary eVent fabric base—eliminating the need for purge valves.

One word of caution: the Ultra-Sil fabric is not designed for external use (i.e. on the outside of a backpack or bikepacking rig). If the use you have in mind requires external mounting, choose the eVac Compression Dry Bag LW.

Size	Weight (oz)	Weight (g)
3 liter	2.0	57
5 liter	2.3	64
8 liter	2.7	76
13 liter	3.3	94
20 liter	3.9	110

If the item(s) you intend to pack is/are at the upper limit of the volume shown in the Size column, it is often better to choose a size larger (this is especially true for use in very cold weather). 

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LIGHTWEIGHT + NOT WATERPROOF: ULTRA-SIL COMPRESSION SACK

Choose it if: you need a lightweight compression sack and water resistant (rather than waterproof) is adequate.

Thanks to our PFC-free, bluesign-Approved 30D Ultra-Sil fabric, the Ultra-Sil Compression Sack compresses your gear down without adding noticeable weight. It’s designed to compress evenly and a slippery finish on the fabric makes it easy to shove into the tight spaces of your pack.

Size	Weight (oz)	Weight (g)
5 liter	1.9	53
8 liter	2.3	64
13 liter	2.9	82
20 liter	3.4	96
35 liter	4.2	118

If the item(s) you intend to pack is/are at the upper limit of the volume shown in the Size column, it is often better to choose a size larger (this is especially true for use in very cold weather).

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COMPRESSION SACKS AREN’T FOR LONG-TERM STORAGE

Compression sacks are great on the trails but make sure not to store your sleeping bags or down jackets in them for too long. The compression can damage the delicate clusters of down or synthetic fill.

DURABLE + NOT WATERPROOF: LIGHTWEIGHT COMPRESSION SACK

Choose it if: you need compression, water resistance, and durability.

Our bluesign-Approved, RCS-recycled, PFC-free 70D Lightweight Compression Sack offers an excellent strength-to-weight ratio, making it our most durable water-resistant compression sack. Four extra-long straps compress bulky items evenly, and a nylon webbing pull-handle makes it easy to remove from your bag.

Size	Weight (oz)	Weight (g)
5 liter	2.4	68
8 liter	3.0	86
13 liter	4.0	112
20 liter	4.7	134
35 liter	5.9	167

If the item(s) you intend to pack is/are at the upper limit of the volume shown in the Size column, it is often better to choose a size larger (this is especially true for use in very cold weather).

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PACKING SLEEPING BAGS AND INSULATED JACKETS: THE EVAC DRY BAG

Choose it if: you need waterproof protection but don’t need maximum compression.

The eVac Dry Bag compresses a little differently to our other bags. Pack your soft items in the bag, roll and click the roll-top closure closed, then sit on the bag to squeeze out air through the eVent fabric base. It doesn’t need straps and a lid to compress; instead, simply roll the roll-top closure down tighter until you’ve achieved a reasonable degree of compression. You’ll need to pack the bag into your backpack and pack other gear on top to prevent it drawing air back into the sack-but it helps you maximize useable space in your bag, and of course, it keeps your gear and clothing dry.

70D PFC-free, bluesign-Approved, RCS recycled nylon and just a touch of Sea to Summit genius. 

Size	Weight (oz)	Weight (g)
3 liter	1.5	43
5 liter	1.8	50
8 liter	2.1	60
13 liter	2.5	72
20 liter	3.4	95
35 liter	4.0	113

If the item(s) you intend to pack is/are at the upper limit of the volume shown in the Size column, it is often better to choose a size larger (this is especially true for use in very cold weather). 

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Compression sacks make hauling gear around so much easier—and, fortunately, there’s one for almost every kind of adventure. If you need the dry storage without the compression, reach for a dry bag instead. Too easy.