Synthetic vs Down Sleeping Bag: Which Is Best?

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Synthetic vs down sleeping bags -- what's the difference and which should you get? We break down this critical piece of survival gear.

comparison of down vs synthetic sleeping bags to determine which is best

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Few pieces of camping gear are as critical for your comfort and survival as your sleeping bag.

The right sleeping bag will provide padding against the ground, insulate you from the cold, and ensure you are awake and refreshed the next day.

The wrong sleeping bag can be cumbersome, uncomfortable, and may lead to a long, cold, sleepless night.

When you’re shopping for your new sleeping bag, you’ll have to choose between two different types:

  • Synthetic sleeping bags
  • Down sleeping bags

Do you know the differences between the two?

You’d better because each type is suited for a different camping experience.

Let’s begin our comparison by looking at the benefits of synthetic vs down sleeping bags.

Benefits of Synthetic Sleeping Bags

Synthetic sleeping bags are made of man-made materials, generally a type of polyester. They have the following benefits:

  • Dry more quickly
  • Non-allergenic
  • Better insulation in wetter conditions (usually)
  • Usually less expensive

Benefits of Down Sleeping Bags

Down sleeping bags are made of animal down or feathers. Usually, it’s either goose or duck down. These sleeping bags have the following benefits:

  • High-quality down bags can be much lighter for the same temperature rating
  • Compress more easily
  • Better insulation in dry conditions
  • Longer lifespan when treated well

Goose down usually makes higher-quality sleeping bags due to its ability to provide the same insulation with less down (meaning less weight). This is called “fill power.”

However, duck down is used more frequently because it’s more readily available and therefore less expensive.

Related: 7 Best Cold Weather Sleeping Bags for Sub-Zero Survival

Choosing between synthetic vs down sleeping bags

How Does a Sleeping Bag Work?

Sleeping bags create a boundary between your body and the environment, trapping a pocket of air. Your body heat warms this air pocket, which insulates you and keeps you warm. Sleeping bags with better insulation trap more air and are better able to prevent this air from escaping through the bag, thus keeping you warmer.

How come two sleeping bags with the same size, shape, and weight can provide two different levels of insulation?

So, what makes one sleeping bag better than another?

  • It provides better insulation per unit weight
  • It’s more durable
  • It suits your specific needs

Regarding that last bullet point, well, more on that in a minute.


How does moisture affect synthetic and down sleeping bags?

Why Does Moisture Negatively Affect Down Sleeping Bags?

Remember how sleeping bags work to insulate you?

(You should. I just explained it like 15 seconds ago.)

Sleeping bags insulate you by using your natural body heat to heat the air and then trapping that warm air next to your body.

Well, trapping air is what makes down sleeping bags so great. The down feathers create a ton of tiny air pockets between the feather plumes, which means a ton of tiny, heated air pockets.

But do you know what happens when feathers get wet?

Those plumes clump together.

Clumped plumes lead to less trapped air, which leads to decreased insulation.

Water resistant down sleeping bags are treated with a hydrophobic coating to repel water

Can They Make Water Resistant Down Sleeping Bags?

Yes, these are a thing!

Water resistant down sleeping bags require specially treated down feathers.

Why can’t manufacturers just line the entire sleeping bag in waterproof material to keep moisture out?

Because your body produces moisture, too. That moisture leads to damp air inside the bag, which would be trapped by a waterproof exterior!

So that brings us back to those specially treated down feathers.

These water resistant down features are treated with a coating, which works at the nano-molecular level. This coating is hydrophobic, meaning it repels water at the molecular level.

You know how your favorite oil-based salad dressing always separates and needs to be shaken before each use? That’s because the oil molecules are hydrophobic and just don’t play well with water.

Essentially, that’s what’s happening around every plume of a water resistant down sleeping bag.

Choosing synthetic vs down sleeping bags

How to Choose the Best Synthetic vs Down Sleeping Bag

Which type of sleeping bag is best for you?

The answer, as with most things in life: It depends!

To get a better idea, ask yourself a couple questions.

Are you backpacking or car camping?

Backpackers generally need something that’s lighter and more compact. For that, down sleeping bags have the edge.

Are you backpacking or car camping?
Are you backpacking or car camping?

Down sleeping bags tend to provide superior insulation per unit weight.

If you’re car camping, the weight of the bag probably doesn’t matter. It’s not like your car is going to feel that extra pound of weight that a synthetic bag will have versus a similarly rated, high-quality goose down sleeping bag.

What environments will you be camping in?

Will you be overnighting in the rainy Pacific Northwest or the warm, dry American southwest?

Honestly, this is probably the most important question!

What environment are you camping in?
What environment are you camping in?

No matter how much you pay for a top-of-the-line goose down sleeping bag, it’s going to underperform a synthetic sleeping bag if it’s rainy or overly humid.

(Unless you get one of those specially treated ones we just talked about.)

And I bet you’ll be willing to eat the extra weight for a synthetic sleeping bag with comparable insulation to a down sleeping bag if it means it’ll actually keep you warm in damp conditions.

Speaking of keeping you warm…

What temperature rating do you need?

Consider the following temperature ratings:

  • Summer: Above 35°F
  • 3 Season: 10°F to 35°F
  • Winter: 10°F and lower
What temperature rating do you need?
What temperature rating do you need?

Keep in mind most bags will have two EN temperature ratings for Comfort and Lower Limit.

  • Comfort Rating: Temperature at which the bag keeps a cold sleeper (e.g., small woman) warm
  • Lower Limit Rating: Temperature at which the bag keeps a warm sleeper (e.g., large man) warm

If you’re a smaller person, you may not be able to withstand temperatures near the Lower Limit rating.

Conversely, if you’re a larger person you may be very comfortable at temperatures just below the Comfort rating.

Unless you want to have multiple sleeping bags, consider your coldest case camping scenario.

Related: Stay Warm Camping In A Tent With These 11 Tips

Which sleeping bag shape do you need?

The synthetic vs down sleeping bag debate doesn’t apply here, but it’s still an important question to ask.

What shape sleeping bag do you need?
What shape sleeping bag do you need? (source)

Sleeping bags come in 4 main shapes:

  1. Rectangular
  2. Semi-rectangular
  3. Mummy
  4. Double wide

Rectangular sleeping bags are perfect rectangles with 90 degree angles at each corner. Those corners give rectangular sleeping bags the most internal roominess, which also means they take the longest to warm up (all else equal). The major benefit of these bags is you can zip two of them together to create a double wide sleeping bag.

Semi-rectangular sleeping bags are like the rectangular ones but have slightly rounded edges. This decreases the overall size and weight of the bag, as well as the internal roominess. This means it heats up a little faster than a comparable rectangular sleeping bag. These are ideal for backpackers or hikers who can benefit from the decreased weight and increased heating efficiency but don’t want to go with a constricting mummy sleeping bag.

Mummy sleeping bags have significantly tapered corners to hug your feet and head. This gives them their creepily accurate name, plus the lowest weight and best efficiency. The downside of these bags is they can be a little uncomfortable, especially for larger people. Mummy sleeping bags are ideal for backpackers or hikers looking to get maximum insulation per unit weight.

Double wide sleeping bags aren’t going to win any efficiency competitions, but they’re great for casually sleeping two. Many double wide sleeping bags actually zip apart to create two separate sleeping bags, should you want to do the camping equivalent of sending your significant other to sleep on the couch.

You Might Also Like: 9 Sleeping Bag Alternatives For Your Next Camping Trip

Synthetic vs Down Sleeping Bags: Which Is Right for You?

To recap, ask yourself those 4 questions above:

  • Are you backpacking or car camping?
  • What environments will you be camping in?
  • What temperature rating do you need?
  • Which sleeping bag shape do you need?

If your answers side more with cooler, drier environments, go with a down sleeping bag.

If you answers side more with damper, less cool environments, a synthetic sleeping bag may be perfect for you.

So, synthetic or down — what do you think? Comment below with your experiences and preferences!

Photo of author

Bryan Hunter

Bryan is the founder of The Outdoor Authority and an avid outdoorsman who has backpacked through South America, hiked in the Galapagos, and spent countless nights camping all across the United States.