No photo
Kelty Tru.Comfort Doublewide 20
Kelty
20 F, 99 oz of CloudLoft fill, 9 lb 8 oz, with two foot vents and two built-in blankets - the features that give a double any independent temperature control.
Double Sleeping Bag vs Two Singles, for Couples Who Actually Want to Sleep
A double bag is warmer, roomier and more pleasant right up to the night one of you is too hot and the other is too cold. Then it becomes one problem with two people in it.
Trail & Tarp earns a commission from qualifying purchases made through links on this page, at no extra cost to you. Full disclosure.
The three options, and who each suits
The short answer
A purpose-built double is the warmest and most comfortable if you both sleep at similar temperatures. Two singles zipped together is cheaper and more flexible but drafts at the shoulders and hips. Two separate bags is the most versatile and the least romantic, and it is what most experienced couples end up with. The deciding question is not comfort, it is whether one of you runs noticeably hotter than the other.
| Purpose-built double | Two zipped singles | Two separate bags | |
|---|---|---|---|
| Warmth for two | Best; shared body heat, no gaps | Good, with shoulder and hip drafts | Each person's rating, independently |
| Independent temperature | Only if it has split features | Partial | Complete |
| Weight | 9 lb 8 oz for a Kelty Tru.Comfort Doublewide 20 | About 6 to 7 lb for two 3 lb bags | Same as zipped, carried separately |
| Splits between two packs | No | Yes | Yes |
| Works when only one of you camps | Badly | Yes | Yes |
| Washing | One large, awkward item | Two normal loads | Two normal loads |
Why a double is warmer, and why that cuts both ways
Two people in one bag share heat and there are no gaps between them, which is a real thermal advantage over two bags side by side. A Kelty Tru.Comfort Doublewide 20 publishes a 20 F rating, 99 oz of CloudLoft synthetic fill, a 9 lb 8 oz total weight and a fit to 6 ft 6 in, along with two foot vents, two built-in blankets and a zip-off top layer.
Those last three features exist because the manufacturer knows the category's weakness. In a plain double, the two occupants get exactly the same amount of insulation whether they want it or not, and the person who runs hot vents by opening the bag — which cools the person who runs cold. Individual blankets and separate foot vents are how a good double restores some independence. If a double lacks them, assume the warmer sleeper wins every argument.
Zipping two singles together
Most rectangular and semi-rectangular bags from the same maker will zip together if one has a left zip and the other a right. Check three things before assuming it: same zip length, same zip gauge, and opposite handedness. Mummy bags from different brands rarely mate cleanly.
What you get is a large shared cavity with two hoods and two draft tubes, which is a genuinely good arrangement for car camping. What you also get is a cold strip along the zip line, and gaps at the shoulders where two mummy tapers meet. Neither ruins a summer night; both are noticeable in October.
The bigger advantage is optionality. Two Marmot Trestles Elite Eco 20 bags, published at ISO comfort 32.2 F and 3 lb 8.4 oz each, are two independent three-season bags that happen to combine. A double is a double forever.
Whatever you choose, the pads decide the night
Two people in one bag are still lying on two separate insulated surfaces, and body weight crushes the bag's fill flat underneath both of them. If the pads are cold, the bag choice is irrelevant. A MegaMat 10 publishes R 8.1 at 3.9 in thick; a MondoKing 3D publishes R 7.0 at 4.25 in. Two pads strapped or velcroed together also stop the gap opening in the night, which is the most common complaint about sharing a bag. See R-value explained.
The weight arithmetic, if you are carrying it
A 9 lb 8 oz double cannot be split between two packs — it is one object — so one person carries the lot. Two singles at 3 lb 8 oz each weigh less in total and split evenly, which is why doubles are essentially a car camping product.
The exception is the backpacking double quilt, which is a different design: no zips, no hoods, attached to the pads underneath rather than wrapping around them. That is worth knowing about if you walk in as a pair, and the reasoning behind quilts generally is in sleeping bag vs quilt.
Ratings, and reading them for two people
Single bags sold in the US and Europe are usually rated under ISO 23537, which publishes separate comfort and limit figures from a standardized manikin test — a Kelty Cosmic Down 20 publishes comfort 31 F and limit 21 F. Doubles are frequently sold with a single maker's number and no standard named, as the Tru.Comfort Doublewide is with its 20 F.
Treat an unstandardized double rating as optimistic, and plan around the colder sleeper rather than the average of the two of you. The difference between comfort and limit ratings, and why the number on the bag is usually the limit, is unpacked in sleeping bag temperature ratings explained.
What most couples end up doing
Two separate bags, two good pads pushed together and strapped, and a blanket over the top when it is cold. It is less appealing on paper than a double and it survives every scenario: one person camping alone, two people with different thermostats, a bag in the wash, a trip where the gear has to be carried.
Buy the double if you camp together, always, in a car, and you already know you sleep at similar temperatures. That is a real set of people and the double is genuinely nicer for them. For everyone else, the flexible option wins on the fourth trip.
The gear this page points to
No photo
Marmot Trestles Elite Eco 20
Marmot
ISO comfort 32.2 F at 3 lb 8.4 oz. Two of these zip together and also work as two independent bags, which a double never will.
No photo
Kelty Cosmic Down 20
Kelty
ISO comfort 31 F, ISO limit 21 F, 2 lb 7 oz. The standardized rating to compare an unstandardized double against.
No photo
Exped MegaMat 10
Exped
R 8.1 and 3.9 in thick. Two of these strapped together stop the gap opening in the night, which is the real complaint about sharing.
Questions people actually ask
QIs a double sleeping bag warmer than two singles?
Yes, in principle: two people share heat and there are no gaps between them. The catch is that both occupants get the same insulation whether they want it or not, so the person who runs hot vents the bag and cools the person who runs cold.
QCan you zip two sleeping bags together?
Usually, if they are from the same maker with the same zip length and gauge and opposite handedness - one left zip, one right. Mummy bags from different brands rarely mate cleanly, and you get a cold strip along the zip and gaps at the shoulders.
QCan you take a double sleeping bag backpacking?
Not practically. A Kelty Tru.Comfort Doublewide 20 publishes 9 lb 8 oz and cannot be split between two packs, so one person carries all of it. Two singles weigh less in total and split evenly, which is why doubles are a car camping product.
QWhat do most camping couples actually use?
Two separate bags, two good pads pushed together and strapped, and a blanket over the top when it is cold. It handles one person camping alone, two different thermostats, and a bag in the wash - none of which a double does well.
Sources
Every figure on this page comes from a published source. We have not tested this gear, so the numbers are the manufacturer's or the standard body's, not ours. How we research.