The right sleeping bag tops the list of must-pack items for any camping trip. And since even warm days in the mountains turn into chilly nights, a 40-degree sleeping bag can help you stay snug and comfortable.
While all 40-degree sleeping bags come with several layers of insulation to help regulate temperature, you’ll find multiple shapes to choose from, options like removable hoods or sections for warmer weather, and convertible designs that expand into comforters.
Check out our buying guide to learn which sleeping bag is right for you. We’ve also laid out our top recommendations at the end, including the luxurious Kelty Cosmic 40-Degree Down Sleeping Bag, which is constructed of heavy-duty material and comes with a limited lifetime warranty.
Considerations when choosing 40-degree sleeping bags
The best 40-degree sleeping bag will help you regulate your body temperature while you sleep, keeping you cool when it’s warm out and warm when the temperature dips. Features such as temperature ratings, shape, materials, closures, and weight are key to a versatile, comfortable 40-degree sleeping bag.
Temperature ratings
Because 40-degree sleeping bags are primarily meant for summer use, they are designed to accommodate a range in temperatures as warm days turn into cool nights. Temperature ratings vary significantly among models based on construction and materials. While some bags are effective down to 40 degrees, others will stay comfortable down to zero degrees.
Shape
You’ve got three main choices when it comes to sleeping bag shape: rectangular, mummy, and semi-rectangular.
Rectangular:
If you prefer a simpler design without a hood and the option to unzip your sleeping bag like a quilt, rectangular is the way to go.
Mummy:
If you prefer a snug sleeping bag that doesn’t require extra clothing layers for warmth, you’ll want to opt for a mummy bag.
Semi-rectangular:
This shape is a hybrid of rectangular and mummy shapes, with a rectangular body and extra cushioning and coverage in the head area.FeaturesWeight
Packing light is often a priority when you’re camping, and different sleeping bag models vary quite a bit in weight. Some are as light as two pounds, while others weigh in closer to four.
Materials
While the majority of 40-degree sleeping bags are made from polyester, thread count and denier (thread weight and thickness) vary from model to model. Sleeping bags with a higher thread count are warmer and more comfortable. A higher denier results in a sturdier, thicker bag while a lower denier results in a softer, silkier bag.
Insulation
Some models of 40-degree sleeping bags are insulated with down (feathers) while others are insulated with synthetic fibers. Though down is slightly heavier, it lasts longer (and won’t clump up) like its lighter synthetic counterpart. A sleeping bag’s GSM (grams per square meter) indicates the density of its insulation, which determines whether the bag is thick and puffy or more streamlined and compact.
Closures
Most 40-degree sleeping bags come with zipper closures. Some models include extras such as draft guards and Velcro zipper covers. Mummy bags and semi-rectangular bags often come with additional drawstring closures in the hood for extra warmth at night.
Price
Most 40-degree sleeping bags are priced between $20 and $80. On the lower end of the spectrum you’ll find lightweight rectangular bags with synthetic insulation, while pricier bags offer more shape options, superior construction and insulation, and all-weather temperature control.
FAQ
Q. Are any 40-degree sleeping bag models waterproof?
A. While there aren’t any waterproof models available, sleeping bags with higher thread count are water resistant to smaller spills. If waterproofing is important to you, you can use waterproofing spray on the exterior of some bags (always check with the manufacturer first).
Q. How durable are 40-degree sleeping bags?
A. Sleeping bag lifespan depends on insulation materials and frequency of use. Down sleeping bags can last for up to a decade, while bags with synthetic insulation usually wear out after 2 to 3 years with regular use.
40-degree sleeping bags we recommend
Best of the best: Kelty Cosmic 40-Degree Down Sleeping Bag
Our take: Versatile, well-made mummy-style bag that’s ideal for frequent campers.
What we like: Fits campers up to 6 feet 6 inches tall. Thanks to its DriDown technology, sleeping bag won’t get wet in dewy, damp conditions. Heavy-duty fabric with a high thread count.
What we dislike: More expensive than other models.
Best bang for your buck: Coleman’s Sunridge Sleeping Bag
Our take: Lightweight, inexpensive rectangular bag that’s warm enough for fall or spring camping.
What we like: Smooth, snag-free zippers. Warm, soft lining and water-resistant exterior. Light and easy to repack in the carrying case.
What we dislike: Not ideal for adults more than 6 feet tall.
Choice 3: RevalCamp Sleeping Bag
Our take: This lightweight sleeping bag is soft and roomy for extra comfort.
What we like: Warm, soft, and cozy. Weighs just two pounds and is easy to stuff back into its carrying sack. Material is weather resistant. Available in a wide range of colors.
What we dislike: Slick interior material may cause user to feel like they’re sliding around a bit.
Noelle Ihli is a writer for BestReviews. BestReviews is a product review company with a singular mission: to help simplify your purchasing decisions and save you time and money.
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