Big Agnes Anthracite 20° sleeping bag review: cozy, comfortable and warm in temperatures down to zero

The Big Agnes Anthracite 20° sleeping bag is a super-cozy and soft synthetic three season bag that’s easy to carry, a joy to sleep in and keeps you toasty

The Big Agnes Anthracite 20° sleeping bag
(Image: © Craig Taylor)

Advnture Verdict

The Big Agnes Anthracite 20° sleeping bag is super soft and very warm – ideal for hiking and backpacking trips when the temperature could drop to around freezing.


  • +

    Very comfortable

  • +

    Excellent zipper

  • +

    Reliably warm


  • -

    Pack size is quite large

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Big Agnes Anthracite 20° sleeping bag: first impressions

The Big Agnes Anthracite 20° sleeping bag is a very comfortable, lofty and warm three-season sleeping bag from Colorado-born Big Agnes. Manufactured from a fully recycled shell and filled with FireLine Pro Eco recycled synthetic insulation, the bag is designed to be a reliable and environmentally friendly sack to fall asleep in after long days out on the trail.


• List price: $140 (US) / £159 (UK) when bought directly from Big Agnes
• Weight: 1.24kg / 2lbs 12oz (for the regular size)
• Fill: Recycled synthetic materials
• Comfort rating: 0℃ / 32℉
• Limit: -23℃ / -9℉
• Compatibility: Backpacking, trekking, three-season camping

In classic mummy style, this bag features a large hood that can be cinched down tight in cold conditions, a wide shoulder baffle to trap in heat and a large zip along the length of the bag that comes with a huge loop suitable for opening and closing when you’re wearing a pair of chunky hiking gloves.

The Big Agnes Anthracite 20° is designed to keep you warm in temperatures hovering around freezing. With a lower limit of -6°C / 22°F and an extreme rating of -23°C / -9°F, you can be confident that this bag will perform well in three-season conditions, though you may want to invest in something considerably warmer for the coldest winter nights.

The Big Agnes Anthracite 20° sleeping bag next to tent in the woods

The Big Agnes Anthracite 20° sleeping bag on a wild camp in Bannau Brycheiniog (Image credit: Craig Taylor)

When it comes to the bag’s weight, however, the Anthracite 20° comes in at a rather heavy 1.24kg. While this means the bag is absolutely not lightweight, it’s clearly comparable to other models out there that deliver similar temperature ratings, such as The North Face Cat’s Meow.

And the same applies to its compressibility: the Anthracite 20° comes with a tube-like compression sack that does a reasonable job at reducing its size, though we found that you can compress it down much smaller if you resort to using a dry bag as a vacuum pack and properly squeeze all the air out of the bag.

Big Agnes Anthracite 20° sleeping bag: in the field

The Big Agnes Anthracite 20° sleeping bag in stuff sack size comparison with foot

The Big Agnes Anthracite 20° packed back into its stuff sack (with boot for size comparison) (Image credit: Craig Taylor)

To test the Big Agnes Anthracite 20°, I used it on several occasions through the end of summer 2023 and into fall. I used it on a rainy night in Bannau Brycheiniog National Park and a couple of times out on Dartmoor where I hiked around 15km before getting set up. Each time, the temperature dropped down into single digit conditions, with the night in the Brecon Beacons topping out at around 7°C. I never once felt cold in the Anthracite 20°, which shouldn’t be any major surprise considering it didn’t come close to the extremes this bag is supposed to be able to handle. 

The Big Agnes Anthracite 20° sleeping bag label

The Big Agnes Anthracite 20° sleeping bag’s temperature ratings (Image credit: Craig Taylor)

Which, unfortunately, remains a bone of contention for me, forcing me to raise an eyebrow every time I look at the bag, especially considering the decision to attach a large label with Anthracite 20°F / -7°C written in bold across the front of it. As is the case with most sleeping bag manufacturers, Big Agnes seem to have opted for marketing over function here, as there’s simply no way I’d take this bag down to such extreme temperatures. Even their own internal benchmarks have the bag’s lower limit listed as -6℃, for example. That being said, I’d be confident in taking this thing down to freezing as long as I used it with a suitable sleeping pad – and I’m a remarkably cold sleeper.

The Big Agnes Anthracite 20° sleeping bag on a tree branch

Airing out The Big Agnes Anthracite 20° sleeping bag (Image credit: Craig Taylor)

In regards to the design of the bag, Big Agnes have included some clever features to ensure you keep warm in the places you need to keep warm most. The back of the bag comes with noticeably less insulation, for example, while the top of the bag feels about twice as thick. What’s more, the zipper is almost the full length of the bag, stopping only about 25cm above the foot box. This means you can open the bag almost into a blanket of sorts, adding an extra layer of versatility to the Anthracite 20° and helping you to keep a little cooler when camping at warmer temperatures. 

Another thing I appreciated is the oversized toggle on the zipper itself: despite being too small for thick mountaineering gloves, I found I could easily open and close the zipper while wearing a pair of thinner gloves.

The Big Agnes Anthracite 20° sleeping bag in stuff sack

The Big Agnes Anthracite 20° sleeping bag packed up and about to roll into a stream. Possibly (Image credit: Craig Taylor)

When it comes to the bag’s length, I’m 5ft 10in (177cm) and found the regular size to be plenty long enough for me. The baffles captured my shoulders really well, and I could comfortably cinch everything down to trap in as much heat as possible.

Craig Taylor

Growing up just south of the glorious Brecon Beacons National Park, Craig spent his childhood walking uphill. As he got older, the hills got bigger, and his passion for spending quality time in the great outdoors only grew - falling in love with wild camping, long-distance hiking, bikepacking and fastpacking. Having recently returned to the UK after almost a decade in Germany, he now focuses on regular micro-adventures in nearby Snowdonia and the Brecon Beacons, as well as frequent trips to the Alps and beyond. You can follow his adventures over on komoot.