Sleeping Pad R-Values Explained

Why Your Sleeping Bag Isn't Enough to Keep You Warm

Have you ever been cold while camping? Most of us have. It's easy to turn first to the sleeping bag or quilt and bemoan its temperature rating, but the issue may not be what's wrapped around you, but rather what is underneath you.

I use a 10° quilt, which means if the outside temperature gets down to 10°, I will survive the night. Maybe not comfortably, but I'll live. The main reason I use a quilt instead of a sleeping bag is because the side of the sleeping bag that would be underneath my body isn't keeping me warm; the weight of my body compressing the down renders the material ineffective in terms of heat retention, so removing the side that isn't helping me stay warm helps eliminate space and weight in my pack. When I first started backpacking, I didn't quite understand that my sleeping bag wasn't the sole piece of gear responsible for keeping me warm overnight. On a camping trip in the Upper Peninsula of Michigan with some friends in 2019, I actually didn't bring a sleeping pad, claiming that my 25° sleeping bag would be enough for June on Lake Superior. It was not. And it's not the bag's fault.

The real culprit? My sleeping pad.

(Or lack thereof.)

The ground beneath you saps body heat like nobody's business. Even in the summer, a buffer between your body and the ground can mean the difference between a good night's rest and an all night shiver-fest. That's where sleeping pads come in. They provide a barrier between your body and the ground, preventing heat transfer up to a certain point.

Understanding sleeping pad insulation can make or break your next camping trip, so let's get into it.

What Is an R-Value?

Sleeping pads are measured by their R-value, which is a measure of thermal resistance between your body and the ground outside. R-values in most sleeping pads (unless you're doing some high alpine mountaineering expedition in the winter) range from 1.0 to 6.5. A higher R-value indicates a warmer sleeping pad, and a lower R-value indicates more heat being transferred to the ground beneath you.

R-value scales are linear and easily manipulated. A sleeping pad with an R-value of 2.0 has twice the thermal resistance of a sleeping pad with an R -value of 1.0 and half the thermal resistance of a sleeping pad with an R-value of 4.0. Sleeping pads can be combined to create higher R-values. If you put a foam sleeping pad with an R-value of 2.5 under an inflatable sleeping pad with an R-value of 4.5, you'll be sleeping toasty warm with a combined R-value of 7.0.

Inflated vs. Closed-Cell Sleeping Pads

There are two predominant types of sleeping pads: inflatable and closed-cell. They both have their pros and cons, and everybody has their own gear preferences.

Inflatable Sleeping Pads:

As the name suggests, these need to be blown up at night and decompressed in the morning before being stuffed back in your pack. They tend to be a little heavier, but they can be folded or rolled into a smaller size, so they're not always taking up their maximum amount of room in your pack. Most of the time, they have a higher R-value, as the air inside the pad creates a solid barrier between your body and the ground. The main downside is that they can malfunction if punctured. While many inflatable sleeping pads come with repair kits, most patch-ups can't happen unless you have access to a tub of water to detect where the hole is, and some leaks (like in the valve) aren't repairable. Plus, if it happens in the middle of the night, you aren't just going to spend time fixing your gear; you're just going to inflate it every time you wake up on the ground in the middle of the night. Some companies have limited warranties on their sleeping pads, but eventually, you'll probably have to replace it.

One of my least favorite camp chores has always been blowing up my sleeping pad, but there are now some sleeping pad pumps on the market that make this chore a lot easier. I use the Alpenglow Gear Alpenblow Micro Inflator, which is very lightweight but not as strong as the slightly-heavier FLEXTAIL Zero Pump 2.

Closed-Cell Sleeping Pads:

These kinds of sleeping pads are great for a variety of reasons, especially if pack weight and finances are big concerns. They tend to be less expensive, more durable, and less weight. Setup and packing take no time at all because it's basically just a big, foldable foam pad that accordions to its minimum or maximum size in seconds. You don't need to spend time and effort on blowing it up, and you certainly don't need an additional device to assist. It's more versatile than its inflatable counterpart as well; it can be used during the day as a sit pad or a yoga mat, and you can easily put it underneath another sleeping pad to increase the R-value. The tradeoffs are size and its own R-value. Most people carry these on the exterior of their packs because they're too large to fit inside, even at its smallest size. They also tend to have much smaller R-values than inflatable pads, as there isn't a buffer of air between your body and the ground. However, once you have one, you're probably not going to need to replace it for a very long time.

Comparison of Popular Backpacking Sleeping Pads

While this is not a comprehensive list of sleeping pads on the market, or the only ones that are used in thru-hiking or ultralight backpacking, these are the ones I've seen most on the trail.

	Type	R-Value	Weight	Price
Therm-a-Rest NeoAir XLite	Inflatable	4.5	Short: 11.5 oz Regular: 13 oz R. Wide: 16 oz Large: 17 oz	Short: $199.95 Regular: $209.95 R. Wide: $219.95 Large: $239.95
NEMO Tensor Trail Ultralight	Inflatable	2.8	Regular: 13.9 oz R. Mummy: 13 oz R. Wide: 17 oz Long Wide: 18 oz	Regular: $189.95 R. Mummy: $189.95 R. Wide: $199.95 Long Wide: $219.95
Sea to Summit Ultralight XR	Inflatable	3.6	Short: 13.8 oz Regular: 14.6 oz Large: 18.7 oz	Short: $139.00 Regular: $149.00 Large: $169.00
Exped Ultra 3R	Inflatable	3.2	Medium: 16.5 oz M. Wide: 18.5 oz Long Wide: 20 oz	Medium: $169.95 M. Wide: $169.95 Long Wide: $169.95
Zenbivy Flex Air Mattress	Inflatable	4.8	20x72 Tapered: 20 oz 25x72 T.: 24 oz 25x78 T.: 25 oz 25x72 Rectangular: 26 oz 25x78 R.: 28 oz	20x72 Tapered: $209.00 25x72 T.: $219.00 25x78 T.: $219.00 25x72 Rectangular: $219.00 25x78 R.: $219.00
Klymit Static V2	Inflatable	1.3	One Size: 16 oz	One Size: $74.99
Nemo Switchback	Closed-Cell	2.0	Short: 10.5 oz Regular: 14.5 oz	Short: $54.95 Regular: $59.95
Therm-a-Rest Z Lite Sol	Closed-Cell	2.0	Small: 10 oz Regular: 14 oz	Small: $49.95 Regular: $59.95

How Do I Choose the Best Sleeping Pad for Me?

As with all gear, this is a highly personalized and individualized decision. Consider the following:

• activity (camping, thru-hiking, backpacking, car camping)

• season/weather (winter conditions and expeditions will likely require different gear)

• cost

• weight

• personal sleeping temperature needs

When I'm car camping, I can get away with a heavier, bulkier pad than when I'm backpacking because I don't have to carry it. I've only camped on snow-packed ground a couple times, and I don't seek it out or prefer it, so I'm happy to have a 3-season pad instead of one fit for winter expeditions. I personally sleep really cold, and I don't mind a few extra ounces of gear if it'll keep me cozy at night. I use the Therm-a-Rest NeoAir XLite, and I don't foresee that changing for a long time. My husband, on the other hand, can get away with a sleeping pad with a lower R-value than I can because he doesn't need as much thermal resistance between his body and the ground to be comfortable. He uses an older model of the Klymit Static pad.

As with most pieces of gear, it's hard to make an exact call for what's right for you without testing them out. Just because I love my NeoAir XLite doesn't mean it's perfect for you, and that's true with any gear list online. Try your best to figure out what kinds of specs matter most to you, borrow gear where you can before buying, and don't get discouraged if something isn't perfect right away. Most of the links above are to REI's products, and they have an awesome return policy, and items that end up being returned after use can be found for much lower prices than new (plus, employees will test out the inflatable ones and determine if they need to be patched or not).

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