Sleeping Bag

General Information

Generally, a quality sleeping bag is essential if you plan to sleep outdoors or in a tent in cool climates—or colder. Otherwise, there’s no need to burden yourself with an expensive, warm, and bulky sleeping bag. However, even if you intend to sleep indoors, a lightweight sheet or sleeping bag (inexpensive) will always come in handy—if only because of the state of some hotel bedding or the lack of blankets in second-class sleeper trains.

How to Choose Your Sleeping Bag?

To stay in shape during the day, it’s essential to sleep well at night. Clearly, the quality and wise choice of sleeping gear—especially the sleeping bag—are crucial to the success of a hike, expedition, or even just any trip. And as with anything, it’s useful to know the key criteria and basic principles beforehand...

Staying Warm

Principle

A sleeping bag’s role is to keep its occupant warm. Since this warmth comes directly from the person inside, the bag’s purpose is to retain it in a confined space while minimizing heat loss.

A sleeping bag’s quality primarily depends on the layer of air trapped within the filling. It’s therefore important to consider the difference in volume between the bag compressed in its stuff sack and when it’s unpacked. The greater this difference, the better the bag’s performance. Also note that the top of a sleeping bag is always warmer than the bottom, which is compressed by the body’s weight.

Key Criteria

On cold or damp ground, an insulating layer—preferably low-compressibility (sometimes included in certain sleeping bags)—can be useful, potentially "saving" up to 10°C. Similarly, accessories like bivouac covers, overbags, or sleeping bag liners can enhance a bag’s specific features.

Since warmth primarily comes from the body and the bag retains it in a confined space, "mummy" bags will always outperform "blanket" bags at the same specifications. Beyond shape, choose a model with a good length (about 20 to 30 cm longer than your height). Finally, materials and manufacturing methods also play a significant role in thermal performance.

Filling

Without going into detail, there are two types of fillings: "natural" and "synthetic."

Natural Filling

Genuine goose or duck down is comfortable and protective. It allows the body to breathe well and generally offers good performance. This filling is particularly useful in low to very low temperatures. Other advantages: lightweight and excellent compressibility.

However, at the same specifications, these down bags are often more expensive than synthetic ones, especially in the lower price range. They also require more care in maintenance and are quite sensitive to moisture.

Synthetic Filling

Synthetic fillings are now used for both basic sleeping bags and those designed for high-altitude mountaineering. Today, they make up the majority of sleeping bags. While some fibers can match the thermal qualities of genuine down, synthetic bags generally remain heavier.

Construction

For the same filling, different manufacturing techniques yield varying performance.

The "classic" system is the simplest, least expensive, but also the least effective. Here, stitching goes through both layers of fabric, creating cold spots. To address this, some manufacturers add an outer fabric layer without stitching.

Double or triple independent baffle systems (two or three bags nested inside each other) are the most effective, though heavier. This method is used for extreme-condition sleeping bags.

The fabrics used each have specific characteristics—weight, waterproofing, tear resistance, etc.—which naturally affect the bag’s thermal qualities, as well as its weight and price.

Two Shapes

"Blanket" Shape

This is the rectangular sleeping bag, with or without a hood, which can be fully unzipped to form a blanket. These bags are roomier but generally heavier and bulkier than mummy bags. However, at equal quality, they are often cheaper.

"Mummy" Shape

This shape features a tapered design at the feet and includes a hood. Some, called "anatomical mummy" bags, conform closely to the body, enhancing the bag’s performance. Better suited for carrying and warmer at the same specifications than blanket bags, "mummy" bags are popular among hikers and mountaineers.

Note that regardless of shape or model, most sleeping bags can be zipped together (making a double-wide bag unnecessary).

How to Choose?

First, by knowing your needs—based on expected weather conditions (temperature, humidity, wind), type of shelter (camping, bivouac, hard surface, with or without a mat), mode of transport (carrying or vehicle), and your own cold tolerance.

Also remember that while each bag is rated for a certain temperature, this represents the limit for spending a night without major issues. It’s best to subtract 5 to 10°C from this rating to determine the real maximum comfort zone, especially since there are still no official standards for measuring a sleeping bag’s minimum usable temperature, and each manufacturer sets its own tests.

Models by Temperature Range

Up to +10°C

Prices range from under 20 € to 60 € depending on shape (usually "blanket") and other features. They are typically 75 cm wide, 1.80 to 2.00 m long, and weigh 1 to 1.5 kg on average (about 35 cm in diameter when packed).

Despite this, these classic synthetic-filled bags offer limited outdoor use. However, they work well as a backup sleeping bag for questionable bedding or train travel.

From +10°C to -5°C

Expect to pay around 50 € to 150 € for mostly mummy-shaped bags. Often slightly wider than the previous category (80/85 cm) and longer (2.00/2.40 m), some can be less bulky when packed. Weight varies from lightweight models (1 kg or less) to heavier ones (1.5 to 2 kg), regardless of price.

These bags are the most versatile for many travelers. They suit various uses and bivouacs during "classic" hikes or treks.

-5°C and Below

For extreme conditions (down to -50°C!) and correspondingly high prices—from around 110 € to 750 €. Almost always, these are baffled mummy bags with down or synthetic fillings offering the best guarantees.

Additional Tips

Protection

To protect yourself or your sleeping bag, you can choose from various accessories like liners, blankets, overbags, and mattresses.

Stuff Sack

Except for the cheapest models (and even then), sleeping bags usually come with a stuff sack. If not, get a waterproof one or make one waterproof (a trash bag can work in a pinch, but still...). Typically, they measure around 30/45 cm long with a 25/45 cm diameter, priced around 15 € or less. Note that in this price range, there are stuff sacks with compression straps to save space—a highly recommended system. If the sack lacks them, consider adding straps or a drawstring for this purpose.

Where to Pack Your Sleeping Bag in Your Backpack?

Inside if you have space, otherwise under the flap. The best space-saving option is at the top of the backpack in the straps designed (or improvised) for this. Other external options include using the backpack’s available straps or loops.

Where to Buy?

Of course, except perhaps for the first category, it’s best to buy your sleeping bag from specialty stores where you’ll find a wider selection and advice from experienced staff.