How to Choose the Right Sleeping Bag?
A warm, restful night under the stars starts with the right sleeping bag.
With so many options, it’s easy to lose sleep even before you hit the trail.
This guide makes the choice easy by breaking down your options, and showing how to pick a bag that fits its job.
Let's unpack everything you need to know.
Here is what you will read in this article.
Table of Contents:
A warm, restful night under the stars starts with the right sleeping bag.
With so many options, it’s easy to lose sleep even before you hit the trail.
This guide makes the choice easy by breaking down your options, and showing how to pick a bag that fits its job.
Let's unpack everything you need to know.
Here is what you will read in this article.
Table of Contents:
1- Temperature Rating & Warmth
It all starts with temperature and warmth. Determining the right warmth level means considering both expected temperature and how you respond to cold.
Start by considering the coldest temperature you might face. Australia’s climates vary widely, so use the chart below to find the typical overnight low for your climate zone and hiking season.
Now you’ve got the overnight low, here’s how temperature ratings work and why the number alone isn’t the whole story.
How to Use Temperature Ratings?
Most bags list either an EN 13537 or ISO 23537 temperature rating, which are standardised lab tests for sleeping-bag warmth (ISO 23537 replaced the older EN 13537). These tests produce a range of values that let you compare bags across different manufacturers; each bag carries three numbers:
- Comfort: The temperature at which a cold sleeper might sleep comfortably.
- Limit: The temperature at which a warm sleeper might sleep comfortably.
- Extreme: A survival rating. Not recommended for planning warmth.
Think about whether you usually sleep hot or cold; unless you know you sleep hot, plan by the Comfort rating.
Tip: If you tend to pile on blankets at home, that means you are a cold sleeper. Choose a bag rated a little lower than the forecasted low. If you often feel hot and throw off blankets, you’re probably a warm sleeper. Your body naturally produces more heat, so you may feel comfortable in conditions that seem chilly to cold sleepers.
An ISO/EN rating isn’t a guarantee. Your real-world warmth depends on factors such as body size, age, metabolism, health and the layers you wear. Also, if your bag is too roomy, you’ll feel colder than the label suggests. Ratings assume a close fit; extra length or girth creates cold pockets you’ll notice when you turn.
Remember that the ISO 23537 lab test puts a thermal mannequin in mid-weight base layers on a mat with an R-value of 4.8; if your mat’s R is lower or your clothing is lighter, you can’t expect your bag to achieve the rated temperature.
Tip: If you want one bag for all conditions, lean towards warmer. However, many of the warmest bags lack venting features, so prioritise options that let you manage heat by unzipping, opening the footbox, or using it quilt-style when nights are mild. See section 4- Features and Considerations.
2- Shape
Once you know how warm you need, the next thing to consider is the shape.
Closer fits are warmer because your body warms a thin layer of air near your skin, and any dead space adds air to heat. If you are not heading into extreme cold, you may prefer a shape that lets you sleep on your side or move more.
Here are your options:
Rectangular bags are basically quilted blankets with zips and great for people who sprawl. Although they suit sprawlers, the extra space adds air to heat and the wide opening can let warmth escape.
Semi-/tapered rectangular are mostly a rectangular body with only a gentle taper toward the feet, giving enough room for side-sleepers while being noticeably warmer than a full rectangle. A good pick if you change positions and want one bag that works as both bag and quilt in milder conditions.
Mummy bags have the snuggest profile that hugs the body with a pronounced taper from shoulders to a narrow footbox. Mummy designs also have a small face opening. Mummy bags will often mean you’ll sleep mostly on your back and like feeling tucked in.
Quilts are good for huts, vans, or warm nights. Also popular in ultralight setups where the mat and clothing do more of the work. Many have straps to secure around your mat to minimise drafts.
Duo / Zip-together Two-person bags exist, and many standard bags can zip together if you buy left- and right-zip versions. Use them solo or join them when a partner comes along.
3- Understanding Insulation Types
Sleeping bags are filled with either down or synthetic fibres.
Down is lighter for the warmth it provides and packs small, but it loses much of its insulation value when wet and costs more.
Synthetic fill weighs and packs larger yet still insulates when damp, dries faster, and is cheaper, though it compresses and lofts less over time.
Each has its pros and cons. For a detailed comparison, see our Down vs Synthetic Sleeping Bags blog.
4- Features and Considerations
a. Weight and Packability
On long treks every gram counts. Weight-driven models will usually integrate higher-loft down, pared-back zips, a trimmer cut or lighter fabrics.
Sea to Summit’s Spark line is a good example: the Spark Ultralight uses a 10 D shell (many competitors in the same temperature class use 15–20 D) and the result is a sub-one-kilogram winter bag that still carries full-box baffles and a full-length zip.
Also look at fill-power: the higher the number, the larger each down cluster and the more air it traps per gram, so you need less total down for the same warmth. With less fill, the bag weighs less and, because there is simply less material, it squeezes into a smaller stuff sack—handy when pack volume is tight.
Quick tip: Stuff, don’t roll, your bag into its sack; it packs faster and puts less strain on the seams.
b. Zips and Venting
A two-way zip is the simplest insurance against a too-warm night. Keep this in mind when choosing a one-bag-does-it-all.
For example, Mont’s Brindabella runs a full-length side zip plus a separate foot slider so the bag opens flat like a quilt. Being two-way, it also lets you just crack the torso or feet without opening the whole bag.
Step up to the Spindrift, and the single side zip locks heat in but trades away the Brindabella’s open-flat convenience.
c. Baffle Construction
Warmth is only as even as the chambers that hold the down. So the down can loft fully, technical sleeping bag down chambers will use a strip of fabric running between the inner and outer shells, to create a little “wall” inside the chamber. This keeps the shells apart and ensures the heat can’t short-circuit across a seam.
By contrast, sewn-through chambers stitch the two shells together. They’re lighter and cheaper, but each seam leaks heat, so if you plan real winter nights, pick box, I-beam or trapezoidal baffles.
Baffle orientation matters too. Vertical baffles around the torso stop the down from sliding off your chest (where you need it most) and to the sides of the bag.
d. Extra Warmth Suggestions
If cold feet ruin your sleep, you can get a boost by pre-warming the footbox with a hot-water bottle (in a sock) for 10–15 minutes before sleep.
Mont adds a dedicated heat-pack pouch (dubbed Toaster Pocket) in the footbox of the Spindrift, Expedition, Brindabella, Helium and Zodiac lines.
Once inside, snug the draft collar and hood until they just touch to stop warm air pumping out.
e. Backpacking vs Camping Sleeping Bags
Backpacking sleeping bags are built to be light and compressible for hikers who carry everything on their backs. Camping bags, on the other hand, lean into comfort and space, with less concern for weight. They are best reserved for car-based trips where comfort matters more than weight.
Our Top Picks of Sleeping Bags
A highly versatile 3 season sleeping bag that will satisfy the needs of most campers and hikers alike in Australian conditions. We love the arm opening, wide-cut and BlanketZip features of the Comfort Sleeping Bags.
Perfect for trekking, long-distance hikes and all those who need a little extra warmth margin. Women-specific shaping, extra down in the footbox and a holds weight near 1 kg.
Brindabella is an all-time favourite here at K2. A lofty 850 fp fill, two-way zip from top to bottom and a close-fitting collar let it handle everything from frosty alpine nights down south to milder shoulder-season trips up in QLD.
Hamelin offers excellent value with Thermolite Ecomade insulation that keeps warming even when damp, plus a relaxed mummy cut for side sleepers. At around 1.1 kg and priced well under comparable down bags, it’s a smart pick for beginners.
The Exped Ultra -10° is a high-end sleeping bag for those trekkers, fast and light adventurers, and hikers who are looking for the smallest packed size, lightweight sleeping back on the market.
Mont Helium shines for bikepacking and micro-adventures, with vertical baffles that keep the 800 fp down centred over you, and the whole bag compresses to nothing.
Choosing a sleeping bag isn’t complicated once you know what you’re looking for. Use our top-pick lists as a shortcut if you want proven options for typical Aussie conditions. Still unsure?
Drop by K2 or call us—trying a few bags and talking through your trip will lock in the right choice. Sleep sorted, adventure ahead.