A sleeping bag is only one part of your outdoor sleep system. Weather, shelter, ground insulation, clothing and individual comfort all affect warmth. This guide uses manufacturer information and general buying criteria; it does not claim a new hands-on comparison.
What sleeping bag temperature ratings mean
Standardized ISO or EN ratings can include a comfort rating and a lower limit rating. Comfort is a more conservative starting point for many cold sleepers; neither number guarantees warmth for every person. A number in a product name may be a brand estimate or limit rather than the comfort rating. REI’s rating guide explains the distinction.
Plan for a margin below the forecast low, and account for wind, wet conditions and changing forecasts. For serious cold or remote trips, seek appropriate local guidance and bring a suitable backup plan.
Sleeping bags to consider
The Kelty Cosmic Down 20 is listed by its manufacturer with 550-fill down insulation. It is a useful starting point if packed size matters, but compare the exact size’s current specifications, independently stated comfort rating and packed weight with your trip. The model name alone does not establish comfort at 20°F.
For car camping, compare roomier rectangular synthetic bags if space in the car is less important than ease of movement. For backpacking, compare a fitted mummy bag or quilt with an adequate insulated pad. Product availability, price and specifications vary; confirm them before buying.
Choose insulation and fit
| Choice | Advantages | Trade-offs |
|---|---|---|
| Down | Often compressible for its warmth. | Needs protection from moisture and can cost more. |
| Synthetic fill | Often less expensive and easier to manage in damp conditions. | Can be bulkier for comparable warmth. |
| Mummy shape | Fitted shape reduces air space to warm. | Less room for sleepers who move a lot. |
| Rectangular shape | More room and some unzip into a blanket. | Often bulkier and less efficient in cold conditions. |
Check maximum user height, shoulder and hip dimensions, zipper location, hood and return terms. Side sleepers may prefer a wider cut. Fill power is a measure of down loft, not a temperature rating on its own.
Pair the bag with the right sleep system
A sleeping pad insulates you from the ground. Its R-value measures resistance to heat loss; a higher R-value generally means more insulation. Choose a pad appropriate to the expected ground temperature and conditions. REI’s pad guide explains how pad insulation affects the complete system.
Keep your bag dry, use shelter suited to the forecast, and follow its care label. Store it uncompressed when practical to protect loft. A damp or compressed bag can lose insulating performance.
Frequently asked questions
Does a 20°F bag guarantee comfort at 20°F?
No. Find out whether the figure is a comfort rating, lower limit or manufacturer estimate, and include a margin for conditions and personal needs.
Is down waterproof?
No. Water-resistant treatments do not make a down bag waterproof. Protect it from rain and condensation.
Do I need a sleeping pad?
Yes for most camping situations: a pad provides ground insulation as well as cushioning, and affects the warmth of the whole system.