Although ultralight backpackers prioritize weight reduction, an ineffective sleeping bag or quilt that cannot act as an insulator during warm nights loses value. Our most lightweight sleeping bags tested, such as Feathered Friends Flicker 40 UL, feature versatility by acting both as an enclosed hoodless mummy bag and spread-out quilt with flexible foot box features.

Weight

Sleeping bag shapes are key components to providing warmth. A slim mummy-style design can trap more of your body heat inside by restricting space more effectively than expansive rectangular models, but there is only so much warmth it can offer without compromising comfort or making you too cold.

As such, we suggest carefully considering each sleeping bag’s dimensions to see which best suit your height and body shape. You may also wish to visit an REI store nearby and try on multiple sleeping bags until finding one that feels just right!

Sea to Summit Spark 15F offers light weight versatility with its excellent warmth-to-weight ratio thanks to its combination of Hyperdry 850-loft down and thin 10-denier shell fabric. Furthermore, it features plush draft collar and hood to keep you cozy on cool nights as well as full length zipper that is snag resistant.

Warmth

As manufacturers continue to whittle away at weight, the sleeping bag world is becoming lighter. This category specializes in ultralight bags designed specifically for human-powered backcountry adventures, such as backpacking or mountaineering, in temperatures below zero degrees Fahrenheit.

Finding a sleeping bag to meet your temperature requirements and body heat tolerance largely depends on its temperature rating and thickness/lightness ratio. In general, higher temperature ratings mean thinner and lighter bags.

Insulation type plays an integral part in providing warmth-to-weight ratio. Down is lightweight, packs down small and warms up quickly; however, its effectiveness drops with moisture exposure. On the contrary, synthetic bags remain warm even when wet and maintain their shape over time.

The best bags will include features that maximize your natural insulation (such as a full hood and method to strap it directly onto your pad) while simultaneously minimizing unnecessary weight. Mummy-style bags with compact dimensions and contoured hoods for additional warmth tend to excel at this task.

Comfort

Lightweight sleeping bags often sacrifice some comfort in order to save weight, particularly mummy-shaped models that aim to minimize dimensions for optimal warmth and fit.

Some brands have developed innovative designs to ensure maximum comfort and heat retention in cold temperatures. For instance, Feathered Friends Vireo UL features large draft tubes that block cool air from entering through zipper openings as well as a sewn footbox to maximize heat retention in winter temperatures.

Women’s sleeping bags are specifically engineered to better accommodate their frame. Some rectangular models can even be zip together into double bags. Most models feature a “scoop” shape which maximizes leg room while some provide extra room around knees and elbows for side sleepers. Finally, manufacturers offer lightweight fabrics like water-resistant ripstop nylon in 10D or 20D sizes in order to further decrease weight in these models.

Ventilation

Some sleeping bags feature baffles to keep down from shifting during the night and trap heat, while others provide ventilation capabilities. Our best ultralight sleeping bag was the Feathered Friends Flicker 40 UL which could convert from a quilt into a hoodless mummy bag with its dual drawcord neck baffle or simply be unzipped into an all-purpose camp blanket!

Quilt sleeping bags tend to be lighter than their mummy counterparts, with less shell and fill material used in their design and no built-in hood for warmth retention. Unfortunately, quilts may feel restrictive for people who prefer roomier designs such as mattresses. We looked for quilts with full-length zippers and other details that can help ventilate hot nights as well as synthetic insulations that retain warmth even when wet.