Sleeping bags vary in their packed volume, depending on the type of insulation and what shell and liner fabrics they use. So - 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 litres.

HOW DO I DETERMINE THE VOLUME OF MY SLEEPING BAG?

If you’ve bought a Sea to Summit sleeping bag, look up the volume of the bag on our product pages.

If your sleeping bag is from another brand, the size of the stuff sack supplied with the bag may be on the manufacturer's website (or on the product specifications page of a website such as rei.com). The capacity of the stuff sack is equal to the *mildly compressed* volume of the sleeping bag.

If no volume is quoted for the stuff sack:

1. Measure the radius of the circular base and the height of the stuff sack in inches.

2. Multiply 3.2 x the radius x the radius x the height.

3. Now divide by 61 to give the volume in litres.

4. Alternately, measure in centimetres and divide the total by 1000 to calculate the volume in litres.

HOW DO I DETERMINE THE VOLUME OF MY SLEEPING BAG IF I DON'T HAVE THE STUFF SACK?

1. Put your bag in a cardboard box (one which is larger than the bag).

2. Measure the length and width of the box in inches.

3. Press the sleeping bag down firmly until the upper surface is roughly level in the box (the bag is now mildly compressed).

4. Measure the average depth that the bag occupies in inches.

5. Now multiply length x width x depth = volume in cubic inches.

6. Divide the total by 61 = volume in litres.

7. Alternately, measure in centimetres and divide the total by 1000 to calculate the volume in litres.

NOW YOU KNOW THE VOLUME OF YOUR SLEEPING BAG IN LITERS

The sizes of our compression sacks are listed in the Tech Specs section on each compression sack webpage.

Check out our blog post to find out *which* type of compression sack you will need.

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