Choosing the right sleeping bag and sleeping pad for lightweight and ultralight backpacking may seem like a daunting task with all the various ratings and ever-increasing options. We are often advised to first think about what kind of backpacker you are: do you enjoy road trips and camping, or do you hike in a traditional style or do you want to shave as much weight as possible.

In this article, I focus on building the sleep system for lightweight and UL backpacking: choosing a lightweight sleeping bag and sleeping pad. Since your sleeping bag and sleeping pad work together to keep you warm, you should always choose them to be compatible.

In this guide you will find:

• How to choose a light or ultralight sleeping bag?
• How to choose a light or ultralight sleeping pad?
• The sleep system of a lightweight backpacker: tips & tricks

Now that the options have been narrowed down to light and ultralight products, what remains to be considered of the sleep system gear is:

• Warmth / Temperature ratings
• Type
• Weight
• Comfort
• Size
• Price
• Sleep system: equipment together

In lightweight backpacking, the most important selection criteria are warmth and weight. You may have to compromise comfort (but not necessarily) and size affects weight and comfort. The price usually increases as the weight decreases.

It is not possible to define an exact thermal value for the products that would apply to each user, because the sleep system is affected by, for example, air humidity, wind conditions and everyone's own experience of temperature, which can also vary depending on, how you have eaten and slept. To make it easier for the buyer (you) to compare products, different standards have been developed for rating the warmth of products.

Sleeping bags are evaluated according to the test protocol developed in Europe (ISO 23537-1:2022), where the sleeper wears a long base layer and uses a sleeping pad of a certain warmth. The major manufacturers currently evaluate the R-values of their sleeping pads according to the ASTM F3340-18 standard.

Start with warmth

You use the sleeping bag and sleeping pad mostly at night. Think about what kind of backpacking trips you do and how cold the nights are on average on these hikes. Aim for a sleep system that keeps you warm when you sleep in these temperatures.

For the occasional colder night, you can modify the sleep system to be warmer, so don't buy gear 'just in case' for the potential freezing temperatures. I will return to the sleep system and its fine-tuning later.

Read also: What Is Lightweight Backpacking? Packing List and 10 Tips for Going Light

Sleeping bags for lightweight backpacking

Sleeping bags are basically either synthetic or filled with down (a mixture of down and feathers). Down has the best warmth-to-weight ratio of all materials, so lightweight and ultralight backpackers should choose a down product.

Synthetic sleeping bags are almost always heavier and take up more space when packed than down bags. However, there are also light and ultralight synthetic products on the market if you don't want to buy or use animal products.

The RDS marking on the down product is an abbreviation for Responsible Down Standard. It refers to responsibly produced down, meaning that no animals have been harmed in the production process.

Light and ultralight down sleeping bags

What things should you take into account when you are buying a down sleeping bag suitable for lightweight and ultralight backpacking? In order to be able to compare different sleeping bags with each other, it is essential to understand the key figures and values related to down products and sleeping bags, as well as the differences between the different models.

Key points when choosing a down sleeping bag:

• Temperature ratings: Comfort, Limit, Extreme
• Down 'fill power'
• Water-repellent down (hydrophobic)
• Mummy model or straight
• Sleeping bag, hoodless sleeping bag or quilt
• Size (width, height, and zipper on the left or right)
• Weight
• Price

Sleeping bag temperature values: Comfort, Limit and Extreme

Sleeping bags are often marketed with a temperature value, but what does that mean? In practice, there are three different values marked on sleeping bags: Comfort, Limit and Extreme. The temperatures of EN/ISO-marked sleeping bags are classified according to standards, so the temperature values of different sleeping bags are comparable.

1. Comfort, the warmest of the values, is on average, the temperature at which ‘a standard’ woman sleeps comfortably without feeling cold.
2. Limit or Transition Range is, on average, the temperature at which ‘a standard’ man can sleep only slightly cold.
3. Extreme or Risk Range refers to a temperature where there is already a risk of hypothermia. In these temperatures, the sleeping bag should only be used in an emergency.
4. In unisex models, Limit, or the middle value, refers to the temperature at which the standard man sleeps comfortably.
5. The temperature ratings for sleeping bags are based on the use of a sleeping pad with an R-value corresponding to the temperature of the ground, and the use of clothes when testing the sleeping bag.

For example, the Comfort value of my three-season (manufacturer's definition 2.5 seasons) sleeping bag is -4 °C / 25°F, and I sleep with it comfortably at an average temperature of 0 °C / 32°F with a 5.4 R-value sleeping pad and a long merino wool base layer.

• Although there are endless variables that affect the sleeping temperature, temperature rating is the best starting point for choosing the right sleeping bag for you.
• If you are a cold sleeper, you should choose a sleeping bag with a Comfort value a few degrees colder than the temperature where you sleep.

Down sleeping bag 'fill power'

The Fill Power (FP) or CUIN (cubic inches per ounce) number of the down describes the relative quality of the down in terms of its loft and filling power. Common numbers are 650, 700, 800 and 850, with the highest number representing the highest quality. This number alone does not tell how warm the sleeping bag is.

When defining the warmth value of a down sleeping bag, another number is also needed: the weight of the filling (fill weight), which is expressed in grams/ounces. The higher the FP/CUIN, the less down is needed to achieve the same warmth.

• In other words: warm ultralight down sleeping bags always have a high FP/CUIN, i.e. high warmth in relation to weight.

As an example of comparing numbers and values related to down, here are two sleeping bags of the same warmth ratings and size (regular):

• Marmot Sawtooth FP 650+ / filling 700 g / weight 1310 g
• Sea to summit women's Flame 3 FP 850+ / filling 440 g / weight 665 g

Water-repellent down

When the down product gets wet, it loses its loftiness and thus its insulating or warming properties. Many manufacturers have started to use the so-called hydrophobic, water-repellent down. The down is treated with special chemicals, so that the down retains its thermal insulation properties longer in humid conditions.

However, water-repellent down does not mean that the product is waterproof, but that it does not get wet as quickly as untreated down. Some manufacturers also have reasons not to use hydrophobic down in their products.

Ultralight mummy sleeping bags

Narrow mummy-shaped sleeping bags have long since overtaken traditional rectangular models. In ultralight mummy bags, extra weight has been trimmed especially around the legs. Although the lighter weight pleases lightweight backpackers, mummy sleeping bags can be too narrow, especially for active sleepers, and those who move around a lot at night.

Some of the ultralight sleeping bags have a 'relaxed mummy' shape. These are especially suitable for women and users with wider hips and those who sleep in a wide position.

• In order for you to sleep comfortably, the sleeping bag should be just the right size. In a bag that is too small, the filling can flatten in places, creating cold spots. In a bag that is too big, you have to use energy to heat up the unnecessary space.
• When you consider the size of the sleeping bag, you should think about your typical sleeping position so that you can sleep comfortably.

An ultralight quilt or a sleeping bag without a hood

In lightweight backpacking and especially in ultralight backpacking, ultralight quilts have become extremely popular. Weight has been reduced in quilts by removing fabric and down from where it would not warm anyway, from the back side. The quilts are also hoodless, and they are often equipped with only a short zipper at the leg end.

The quilt market has grown enormously, and just like sleeping bags, the properties of quilts also vary according to temperature, size, weight and versatility. It depends entirely on your preferences whether you prefer a sleeping bag or a quilt.

When using a quilt, the insulation of the sleeping pad becomes even more important. Most quilts are designed to be attached to the sleeping pad as part of the sleep system. The lack of a hood may also have to be compensated for in cold conditions with an insulating balaclava or similar.

• The lightest quilts can be made lighter than the lightest sleeping bags and can be packed into a smaller space. A sleeping bag, on the other hand, is usually warmer than a quilt.
• The same principles (temperature, size, etc.) of ultralight down sleeping bags apply to ultralight down quilts.
• The best ultralight sleeping bag or quilt is the one with the features that best suit your needs, characteristics and preferences.

Weight and price

In practice, on average: the lighter and warmer the sleeping bag, the higher the price. When you want to optimize your budget, think about the sleeping system as a whole and only choose a sleeping bag that is as warm as you absolutely need. In the weight category, aim only for sleeping bags or quilts under 2 lbs.

I recommend comparing sleeping pads before choosing a sleeping bag.

Light and ultralight sleeping pads

How do you choose the right sleeping pad for lightweight backpacking?

Without experience, you probably don't know how warm a sleeping pad you need. If you are a cold sleeper and when you are hiking in a cold climate, you should naturally choose a warmer pad. The R-value gives a good impression of the insulation properties of the sleeping pad.

What is the R-value of sleeping pads?

The R-value means the thermal insulation of a material or structure. The higher the R-value of the sleeping pad, the better it insulates the cold air rising from the ground. An insulating layer between the sleeper and the ground is also needed in the summer.

For example, Thermarest recommends the following R-values:

• 1-2 for the summer
• 2-4 from spring to autumn (three seasons)
• 4-6 for all seasons (winter)
• 6+ extreme cold (winter, frost)

In addition, there is a +-0.5 range between the R-value classes, depending on the conditions and the user.

Thermarest defines sleeping pads as ultralight when they weigh 0-454 g (0-1 lbs) and very light when they weigh 454-907 g (1-2 lbs). In lightweight and particularly ultralight backpacking, the latter weight category rises to unnecessarily heavy products.

To help you compare sleeping pads, you can use, for example, the manufacturers' own helpers, such as on Thermarest's website. There you can find only Thermarest’s pads, though.

There are three main types of sleeping pads:

• Closed-cell foam pads,
• Self-inflating pads (air-filled) and
• Inflatable (air-filled) pads

Closed-cell foam pads category has the lightest (and thinnest) options, but they are not necessarily comfortable to sleep on. Closed-cell foam pads also take up quite a lot of space when packed.

I did the first solo hike in my life with the closed-cell foam pad Thermarest RidgeRest SOLite. I hardly slept on the hike. I couldn't find a good position and my body didn't seem to relax in any way.

• You may get used to the hard pad, so you shouldn't give up right away (like I did myself), even if the pad feels uncomfortable at first.
• In specialized shops (e.g. shops where you can get materials for DIY/MYOG projects) you can often find closed-cell foam sheets cheaply, but the R-value can be difficult to find out.

Self-inflating pads are often heavier and take up more space when packed.

• A lightweight backpacker should not choose a self-inflating sleeping pad, as equally comfortable but significantly lighter alternatives can be found in inflatable sleeping pads.

Air-filled inflatable pads have grown in popularity in recent years. They pack into a small space and feel comfortable. Many air-filled pads come with a pump sack, which allows the pad to be inflated quickly and easily.

• The best ultralight sleeping pad for most people can be found among inflatable pads.

As an example, my three ultralight sleeping pads suitable for lightweight backpacking:

• Thermarest UberLite Small R-value 2.3 (170 g / 6 oz)
• Thermarest Ridgerest SOLite Regular R-value 2.1 (400 g / 14.1 oz; cut short 270 g / 9.5 oz)
• Thermarest Women's NeoAir XLite Regular R-value 5.4 (340 g / 12 oz)

I also own two pads defined by Thermarest as very light:

• Thermarest NeoAir Venture R-value 2.2. (540 g / 1 lb 3 oz)
• Exped Downmat HL Winter MW R-value 7.1 (620 g / 1 lb 5.9 oz)

Considering my own sleeping pads, comfort is (according to my own experience) directly proportional to weight: the heavier, the more comfortable. Since I hike in rather cold conditions and I'm a cold sleeper and a woman, the optimal R-value is somewhere in the 3-5 range depending on the destination of my three season hikes.

The best choice from my own pads (even if I combine different pads) for three-season hikes and in the mountains is Thermarest Women's NeoAir XLite. The pad is sufficiently warm and very light in relation to its weight. There are more comfortable sleeping pads, but the NeoAir XLite is comfortable enough.

• Lightweight backpackers should aim for sleeping pads of around 500 g / 1 lb 1.6 oz and lighter. This group has several options for different budgets. When you invest in the lightness (and insulation) of the sleeping pad, you can choose a slightly heavier and more affordable sleeping bag if necessary.

The sleep system of a lightweight backpacker

The sleep system includes: the sleeping bag, the sleeping pad and the clothes you are wearing. The combination of these items at different sleeping temperatures, determines how comfortably and warmly you will sleep.

The sleeping bag warms because its filling keeps the cold air away and the warm air generated by your body circulates inside the sleeping bag. The sleeping pad warms because it insulates the cold air rising from the ground.

• The most essential thing, even in lightweight backpacking, is that you can sleep warm enough at night.
• The insulation of the sleeping pad has a significant effect on how warm you sleep - the same sleeping bag can feel cold or warm with different sleeping pads.
• If you only get one sleeping bag and one pad, you can adjust the weight and temperature of the sleep system just by adding or subtracting your clothes.
• If you get a couple of light sleeping pads (one of which is e.g., ultralight closed-cell foam), you can regulate the temperature significantly more. In other words, you can use the set at several different temperatures. This makes sense if you are into backpacking all year round.
• You can also build a sleep system by getting a three-season down sleeping bag AND a warm ultralight quilt. In warmer summer weather, the quilt is comfortably cool, in cold weather you stay warm in the sleeping bag, and in very cold weather you can pull the quilt over the sleeping bag for extra warmth.

Tip: when backpacking, use a little effort when choosing a place for your camp. The sunset view may not be the most optimal.

• Seek shelter from the wind and descend lower on high mountains or fells when you need warmth. Stay away from riverbanks or valley bottoms to minimize moisture.
• When using an ultralight and air-filled sleeping pad, clean up the sharp twigs and rocks from underneath before pitching your shelter.
• Look for a softer spot if using a thin foam pad for a more comfortable sleep (but avoid the temptingly soft mosses and wetlands!)

Some people advice that if you use a colder sleeping pad (lower R-value), you should use a warmer sleeping bag with it and a warmer pad with a colder sleeping bag. I think the latter is the better option.

• You can compensate for the colder sleeping pad with a somewhat warmer sleeping bag, but cold air rises from the ground and the flattened down under your back does not warm you much.
• A cold pad + a warm sleeping bag basically means more weight and a higher price compared to a warm pad and a slightly colder sleeping bag, when you stick to light and ultralight equipment and try to achieve an equally comfortable or warm sleeping system with the combination.
• If your budget is tight, you can get a thin and ultralight (e.g., 150 g / 5.3 oz) cheap closed-cell foam pad / sheet from an outdoor store or other specialty store as additional insulation, and cut it to a suitable size. Often, additional insulation is mainly needed in the back and hip area.
• Regulate the sleeping temperature with the help of clothes. Check the weather forecast before your backpacking trip: it will give you a fairly accurate idea of at least the coming week’s night temperatures. A light down jacket is good additional warmth, as long as it is dry.

Tip: start building a sleep system by finding out what kind of sleeper you are (easily cold or easily sweating, comfortable on a hard or softer surface, calm or active sleeper, etc.) before making expensive purchases. Rent a set and spend the night, for example, in your own backyard or in a local forest at a temperature that corresponds to the average temperature of your hikes. Based on experience, choose warmer or softer items for your sleep system if necessary!