Which summer sleeping bag for a tent? 7 light bags up to about 1 kg

In summer a heavy sleeping bag is a pointless extra kilo in your pack, while one that is too thin ends with a hoodie, a hat and chattering teeth at four in the morning.

Below are seven light sleeping bags of up to about 1 kg, with the weight, comfort temperature and packed size given by their makers and what buyers say about them.

How to choose a sleeping bag and what to look for?

Before you start comparing grams and prices, answer one question: what temperature will you be sleeping in? Not “summer”, but how many degrees it will be at four in the morning where you pitch your tent. A July night by a lake and a July night in the mountains are two different nights. Almost everything else follows from that one number.

• A comfort temperature that matches the coldest night you plan for, with a few degrees to spare if you get cold easily. How to read it is explained below.
• A sleeping mat. The fill under your back is squashed by your body weight and keeps little warmth, so what insulates you from the ground is mostly what you lie on. A warm sleeping bag on a thin mat will still be cold from below.
• A hood and drawcords. A hood pulled tight around your face and a collar around your neck keep warm air inside when you turn from side to side. Leave your mouth and nose outside, because the moisture from your breath stays in the fill. On a warm night, just leave everything loose.
• Length. A bag that is too short squashes the fill at your feet and head, and squashed fill keeps you warm poorly. Check what height the maker designed the size for. Mind the tent as well: if the bag touches the walls when you lie down, condensation will wet it overnight.
• Shape. A mummy bag holds warmth better because there is less air to heat. A rectangular bag gives your legs more room and opens into a quilt. If you toss and turn a lot or sleep on your side, a snug mummy can be a nuisance.
• Zip. A two-way zip lets you air your feet on a warm night without opening the whole bag. A “right” or “left” zip tells you which side the zip is on. This matters mainly when you want to join two bags into one double bag: you then need two matching models with zips on opposite sides.

Pay less attention to the extreme temperature (you do not choose a bag by it) and to labels like “three-season” or “four-season”, because there is no common definition of what they mean. Do not worry about a few dozen grams either. One bag “for the whole year” is always a compromise: in summer it is too warm and needlessly heavy, and in a hard frost it is still too thin. That is why this comparison covers bags for the warm months, up to about 1 kg.

And one thing that is easy to miss: a sleeping bag does not make heat, it only keeps the heat you make. Dry base layers kept only for sleeping and dry socks make a big difference, while clothes damp with sweat draw warmth away even in a good bag. In the morning, if the weather is dry, hang the bag out before you pack it, because overnight it soaks up moisture from your breath and body.

Which sleeping bag is the lightest?

The lightest in this comparison is the Trinordic Somra EN, which the maker puts at 700 g¹. Right behind it are the Grand Canyon Whistler 190 at 725 g² and the Mountrex at 730 g³. You will not feel a few dozen grams in your pack, so with these three it matters more whether you prefer a mummy bag with a hood or a rectangular bag that opens into a blanket.

The heaviest are the Nordmut Askja and the down Naturehike CW400, both about 900 g^{4, 5}. But at the same weight the CW400 is meant for much colder nights. If you are putting together a light camping kit, have a look at the comparison of light one-person tents too.

Down or synthetic?

Down gives more warmth for the same weight and compresses into a smaller sack. Synthetic fill copes better with moisture and dries faster^{5, 6}. This comparison shows it well: the down CW400 weighs as much as the summer Askja, yet its maker gives a comfort temperature of about 5 °C instead of about 15 °C.

For summer nights in a tent synthetic fill is plenty, it is clearly cheaper and it minds the morning condensation on the tent walls less. Down makes sense when you want one sleeping bag to cover spring and autumn as well.

How to read comfort, limit and extreme temperatures?

The EN 13537 standard, now ISO 23537, describes, among others, these three temperatures. Comfort is the lowest temperature at which an average woman sleeps through the night in a relaxed position. Limit is the temperature at which an average man sleeps through the night curled up. Extreme is a survival limit for about 6 hours with a risk of hypothermia, and you do not choose a sleeping bag by it^{6, 7}.

So look at the comfort figure, and if you get cold easily, add a few degrees of margin. Whether you get cold also depends on your sleeping pad, clothing, humidity and the weather⁵. Where the number comes from matters too. None of the seven makers ties its temperatures to a standard for the specific model (Naturehike says in general that it tests selected models to ISO), so treat them as guidance rather than a lab result.

If you are planning your first night under the open sky, read how to have a great night in the woods.

Which sleeping bag takes up the least space in a backpack?

Makers give the packed size in different ways, sometimes as the diameter and length of the sack, sometimes as three dimensions, so this comparison is approximate. The smallest sack belongs to the Naturehike LW180: 13 cm across and 31 cm long in the Large size⁶. Only slightly larger are the sacks of the Mountrex at 28 x 15 cm³ and the Whistler 190 at 15 cm across, 28 cm long and 5 litres². Both Trinordic bags pack to 28 x 16 x 16 cm¹.

The largest are the Nordmut Askja (20 x 35 cm⁴) and the down CW400 (35 x 18 x 18 cm⁵). CW400 buyers say, though, that it squeezes into a very small bundle in its compression sack, and it is still the warmest bag here.

What sleeping bag for a bug-out bag?

In a bug-out bag the sleeping bag sits for months, and you do not know whether you will need it in July or in November. A summer bag with a comfort rating of 15-20 °C will not be enough on a cold night, so a bag rated closer to 5 °C suits such a pack better, or a summer bag plus warm clothes you can sleep in.

Storage matters too. Naturehike advises against keeping either the down CW400⁵ or the synthetic LW180⁶ tightly compressed for long and suggests storing them loosely in a breathable bag, while in a bug-out bag the sleeping bag stays compressed all the time. That is why, in my view, it is worth taking it out every few months, airing it and packing it again.

Sources

1. Trinordic, Somra EN - Ultralätt sommarsovsäck, specifications: trinordic.se
2. Grand Canyon, Whistler 190, tech specs: grand-canyon.dk
3. Mountrex, Schlafsack 730 g, product description: mountrex.shop
4. Nordmut, Sommerschlafsack Askja, specifications: nordmut.com
5. Naturehike, CW400 Down Ultralight Sleeping Bag, tech specs and FAQ: naturehike.com
6. Naturehike, LW180 Synthetic Sleeping Bag, tech specs and FAQ: naturehike.com
7. Deuter, Dreamlite L, temperature ratings to ISO 23537: deuter.com