Sleeping bags: warmth ratings, shape and fill

Start with the coldest part of the trip

Find the expected overnight conditions at the campsite, including its elevation. A forecast for a nearby town may describe a different setting. Think about whether you tend to wake cold and how easily you can change plans if conditions become unsuitable.

Read the rating carefully

Comfort and limit ratings answer different questions. Laboratory ratings provide a comparison point, while actual comfort depends on the person, sleeping pad, clothing and conditions. Do not treat an extreme or survival rating as a comfortable camping target. REI’s buying guide explains how these labels differ.

Compare shape and insulation

A roomy rectangular bag allows more movement; a closer-fitting shape reduces unused space. Down generally packs efficiently but needs protection from moisture. Synthetic insulation is another option, with different packed size, cost and wet-weather trade-offs. Compare the finished product, not fill type alone.

Try the whole bedtime setup

Lie in the bag on the pad you intend to use. Bend your knees, roll to your usual sleeping position and check the zip from inside. Keep fabric clear of the slider rather than forcing it. If you use a hood, check that its adjustment is understandable without covering your breathing space.

Write down the buying decision

• Expected trip conditions and the rating category used for comparison.
• Pad and dry sleep clothing that will be used with the bag.
• The packed space available and any carrying requirement.
• How the bag will be dried, cleaned and stored between trips.