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
Your sleeping bag plays an important role. In very cold conditions it will help protect you from freezing temperatures and cold weather injuries. Otherwise a good night’s sleep is essential for your overall enjoyment: you’ll improve your mood, have more fun and make better decisions in general.
Consider all the variables
How you experience the temperature is very personal. Some people just naturally run a little warmer or colder. Your gender can also make a big difference. In general, women sleep a few degrees colder than men.
You might also feel warmer or colder depending on a few variables. Below is just a few to consider:
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.
Temperature Ratings: What Do They Mean?
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 with distinct benefits.
A mummy sleeping bag is the ideal shape to choose when you need maximum insulation, with 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 move — 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.
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, so it’s far less restrictive than a mummy shape. Unlike the mummy, you can open it up and use it as a blanket which can be beneficial in warmer climates.
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.
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.
- 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.
- 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.
- Can last upwards of a decade, even more if you look after it properly.
- Can suffer in wet conditions. 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.
- 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.
- 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.
- 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.
Nifty features and accessories:
Sleeping bags come with a full scope of cool features including different baffle constructions, draft tubes, neck collars, and two-way zips. But as a beginner, here are a few key accessories 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 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.