A sleeping bag is a technical bit of gear. Depending on your activity, there’s a lot of consideration. What should it be made of? Which is the best shape? And why are temperature ratings written in hieroglyphics?
If you’re new to sleeping bags, this guide will help you make one of the most important outdoor investments you can make.
Why you need to get it right when choosing a sleeping bag
Your sleeping bag plays an important role. In serious cases, choosing the right sleeping bag will protect you in very cold conditions and help protect you from cold-weather injuries. Beyond this, having the right sleep system when hiking or camping will have a range of effects:
- Better sleep will improve your physical recovery each day. Having a poor night's sleep reduces your body's production of cytokines, a protein that targets infection and inflammation.
- The right sleeping bag, mat, and accessories will help prevent injuries the next day. Sleep plays a vital role in temperature regulation, fostering a strong immune system, steady hormone levels, and a good appetite. These attributes all form part of your energy and how you take on a hike each day.
- Having a good night's sleep will simply put you in the right mental space for the next day.
How do you sleep?
How you experience the temperature is very personal. Some people just naturally run a little warmer or colder. Your sex can also make a difference. In general, women's internal clock can be slightly shorter than a full 24-hour cycle sleep that men experience, which means they can tend to wake up earlier and can also sleep at a temperature that is a few degrees colder than men.
You might also feel warmer or colder depending on a number of variables:
Weather conditions: High humidity, rain and snowfall will all have an effect on how you experience the temperature while you’re in your sleeping bag. Factor in any variable weather conditions you may experience on your trip.
General sleeping conditions: Are you sleeping on a sleeping mat? You should be! Laying directly on the floor of a tent will be uncomfortable and cool you down as you lose heat through the ground. Similarly, how you experience temperature will differ between a hut and a tent.
The layers you wear to bed: Typically you shouldn’t wear too much to bed. If it’s cold, a thin base layer with some good socks and a beanie is usually enough. A sleeping bag liner can add another layer of insulation if you need it.
Fuel: If you go to bed on an empty stomach, you’re more likely to feel the cold. Make sure you fuel your body properly so you can generate enough heat – eat well and stay hydrated.
Choosing your sleeping bag's temperature rating
Now that you’ve factored in a few personal considerations, let’s consider the three key temperature ratings on offer.
Most technical sleeping bags follow the international European Standard EN13537 to communicate their temperature ratings. This create three unique temperature categories: T Comfort, T Limit and T Extreme.
T Comfort: Comfort is based on a ‘standard’ adult woman having a comfortable night’s sleep. She’s wearing one base layer in a relaxed position, and you guessed it, she’s comfortable.
T Limit (AKA the lower limit of the Transition range): is based on the lowest temperature at which a ‘standard’ adult male is deemed to be able to have a comfortable night’s sleep. He's also wearing one base layer but sleeps in a curled position.
T Extreme (AKA the lower limit of the Risk range): is a survival only rating for a ‘standard’ adult woman. This is an extreme survival rating only and it is not advisable for anyone to rely on this rating for general use. There will be a strong sensation of cold which can only be endured for a limited time.
These temperature ratings are represented on the scale below:
To choose the right temperature, always base your purchase on the coldest temperature to expect during your trip.
If you’re um-ing and ah-ing over what the weather may or may not do, err on the safe side. Temperature expected to be 5 degrees? Go for 0.
It’s a lot harder to increase your warmth than it is to cool down. In short, you should always aim to choose a sleeping bag in the Comfort or Transition ranges depending on your individual needs.
How to choose a sleeping bag shape
Sleeping bags come in mummy, semi-rectangular or rectangular shapes. All come with distinct benefits.
Mummy sleeping bags
Core feature: maximum insulation + minimum volume and weight.
The mummy shape is narrow at the feet and tighter around your body so there’s less space around you. This is a deliberate design decision — with less empty space to heat up, your body won’t have to work as hard to stay warm. You’ll stay warmer for longer and use up less energy to boot.
A mummy bag also has a snug hood you can pull around your head for extra heat retention.
Semi-rectangular sleeping bags
Core feature: more legroom + usable as a blanket
These bags suit a variety of uses and temperatures and have a tapered cut that still provides efficient heat retention. There’s more space for your legs for those who like to sleep on their side or who move around more in their sleep. Unlike the mummy, you can open it up and use it as a blanket which can be beneficial in warmer climates.
Core feature: better in warmer climates + the most space
Rectangle shapes are as wide at the foot as they are at the shoulders. They give you the most amount of room and are a good choice for warmer climates, camping beds, car camping, or for when you want to share your sleeping bag with someone else.
Note: Make sure you pay attention to the max sleeper height of your sleeping bag as well. As a general rule of thumb, you should add 25–30cm on top of your height for maximum comfort.
How to choose a sleeping bag fill
The two best types of fill for sleeping bags are down or synthetic, and each type offers different advantages.
A down sleeping bag can be appropriate for multi-day overnight hikes, cold camping conditions, world travel or alpine adventures.
- Warmth. It offers you the very best warmth for weight on the market. Nothing will keep you quite as warm for the same weight. If you’re new to down in general, it might be worth understanding what down fill power is and why it matters.
- Lightweight. If weight is an important consideration, down is a better choice.
- Compression. Down sleeping bags are more compact and easier to carry in a backpack or on the move.
- Durability. It can last upwards of a decade, even more if you look after it properly.
- Less water-resistant. To combat this, look for a down sleeping bag with water-repellent down that sheds water and dries quickly. A waterproof outer fabric will help too.
- Price. Typically more expensive than synthetic sleeping bags – but well worth the upfront investment.
A synthetic sleeping bag can be appropriate for a wide range of activities,including an overnight hike, camping, and travel across a range of climates.
- Wet-weather friendly. Synthetic fill performs well even in damp conditions. The lightweight synthetic fibres are less affected by moisture and trap warm air around your body, giving you a high thermal performance even when damp.
- It’s easy to care for. You can easily wash your synthetic bag in the washing machine.
- Weight. Synthetic sleeping bags are heavier, so can add additional grams to your backpack or luggage. That said, if a heavier bag is what you need on your adventure, it’s worth adding the weight to your sleeping kit and taking something else out.
Creating an effective sleeping system
Sleeping bags come with a full scope of cool features including different baffle constructions, draft tubes, neck collars, and two-way zips. But they form just a part of your entire sleeping system that work together to protect you from weather and ensure you enjoy a good sleep when camping or hiking. Here are a few key aspects to your sleeping system that you should keep an eye out for:
A sleeping bag liner
A sleeping bag liner can add another layer of insulation and help keep your sleeping bag cleaner for longer – especially good for down sleeping bags which can be tricker to wash. For cold weather climates, look for thicker liners made from silk or polyester. For warmer weather conditions, opt for something highly breathable like silk or cotton.
A sleeping mat or mattress
In cold temperatures a 4-season sleeping mat is essential. Sleeping directly on the ground sucks the heat right out of your body, so even the most expensive sleeping bag will struggle to help keep you warm. But whatever the weather, a decent layer between you and the floor will just make you more comfortable. Getting a good night’s rest before a long day of hiking shouldn’t be underestimated.
A comfortable pillow
Pillows range in their shape, size and material because, just as we sleep differently and require different shaped sleeping bags and mats to suit our body and sleeping style, pillows can make or break a good night's sleep.
A women’s specific fit
In general, women can sleep a few degrees colder and some sleeping bags will offer additional warmth. For example, our womensFIT sleeping bags include extra down in the torso and foot areas where women are more prone to heat loss. Our womensFIT sleeping bags are also shorter to maximise efficiency and reduce the need to heat empty space. It’s a nice added extra if you really feel the cold.
More from the Summit Journal...
How to choose a sleeping bag
It's one of the most important outdoor investments you can make, so read this post before choosing a sleeping bag.
Understanding the EN Standard for sleeping bags
The coldest time of the day is said to be just before sunrise – when you’ll need a warm sleeping bag.
How to wash a down sleeping bag
Extend the life of your down sleeping bag by properly caring for it.