What R-value do I need?

R-value measures resistance to heat flowing out of you and into the ground, and it is additive, so two pads stack. As a working guide, R-value 2 and below is summer only, R-value 3 to 4 covers warm nights and mild shoulder season, R-value 4 to 5 handles spring and autumn including a light frost, and R-value 5 and above is where you want to be on frozen ground or snow. Those bands are a rule of thumb, not a standard. Note that Exped's own guidance on its site recommends at least 6.5 to get the rated warmth out of a sleeping bag, which is a higher bar than most people apply.

Is an R-value from one brand comparable to another?

Only when both were measured the same way. The industry moved to a shared ASTM test method precisely because in-house numbers were not comparable. Exped labels the Ultra 3R R-value as ASTM measured. Therm-a-Rest publishes 4.5 for the XLite NXT and 7.3 for the XTherm NXT without naming the method on those pages. Where the method is not stated, treat the figure as the manufacturer's claim rather than a certified result.

Does a thicker pad mean a warmer pad?

No. The XLite NXT and the XTherm NXT are both 3 in (7.6 cm) thick and their R-values are 4.5 and 7.3. The difference is internal construction, in this case reflective layers inside the pad, not the distance between you and the ground. Thickness buys comfort, especially for side sleepers and on stony ground. Insulation buys warmth. They are separate purchases that happen to arrive in the same product.

Does the sleeping bag rating already account for the pad?

No, and this is where most cold nights come from. A sleeping bag rating assumes the pad underneath is doing its job. Compressed insulation under your body weight has almost no loft and almost no value, so the pad is carrying that side of the equation alone. Buying a warmer bag to fix a cold pad does not work.

Closed cell foam cannot puncture, costs little, weighs little and gives you an R-value around 2, which is a summer number. Inflatables give far more warmth and comfort per gram and can fail. Many people carry a light foam pad under an inflatable in winter, which adds the two R-values together and gives you a floor to sleep on if the inflatable gives up.

Best sleeping pad for backpacking: R-value 3.2, 4.5 and 7.3 compared

R-value is the number that decides a sleeping pad. Everything else is a tiebreak. Three pads here span 3.2, 4.5 and 7.3, and the specifications come from each manufacturer’s own product page, read on July 20, 2026. We have not slept on any of them and nothing below claims otherwise.

How to choose

Work backward from the coldest ground you expect, not the coldest air. You lose heat to the ground by conduction all night, and the ground does not warm up the way the air does. A clear night in the Pyrenees in September puts frost on the grass while the air sits above freezing. The number you need is set by that surface, not by the forecast low.

Rough bands, and they are rough: below R-value 2 is summer, 3 to 4 covers warm nights and mild shoulder season, 4 to 5 gets you through spring and autumn with a light frost, and above 5 is where frozen ground and snow live. Exped’s own site goes further and recommends at least 6.5 to get a sleeping bag’s rated warmth, which tells you something about how conservative you should be if you sleep cold.

Check the R-values are comparable before you compare them. The whole point of the ASTM method is that a number from one brand can sit beside a number from another. Exped states its figure is ASTM measured. Therm-a-Rest publishes 4.5 and 7.3 on these two pages without naming a method. That does not make the figures wrong, but it does mean you are setting a stated standard against an unstated one.

Then look at what a warmer pad actually costs you. This is the surprise in the numbers. Going from the XLite NXT at R-value 4.5 to the XTherm NXT at R-value 7.3 costs 70 g in Regular, from 370 g to 440 g. That is a very cheap 2.8 R. Going the other way, the Exped Ultra 3R at R-value 3.2 weighs 450 g in M, which is more than the warmer XLite. If the only axis you care about is warmth per gram, the answer is not the pad with the smallest number.

What the Exped gives you instead is different: 65 cm wide sizes, a length up to 197 cm, and the ASTM label. A wide mat is not a luxury if you are 6 ft 2 in or you sleep with your arms out.

Then packed size, then fabric. All three pack small. The XLite NXT is 9 x 4.1 in in Regular, the XTherm 9 x 4.5 in, the Exped 23 x 11 cm in M. The fabric difference is more consequential: Therm-a-Rest puts 30D on both faces of the XLite and 70D on the underside of the XTherm. The underside is the face that meets pine cones, gravel and the stony corner of a stopover. If you are pitching on rough ground and carrying the lighter fabric, carry a groundsheet too.

The short version

Summer and mild shoulder season, and you want a wide mat: Exped Ultra 3R, R-value 3.2, 450 g in M, ASTM labeled.

Spring to autumn, lightest way to a genuinely warm night: Therm-a-Rest NeoAir XLite NXT, R-value 4.5, 370 g in Regular.

Frozen ground, snow, or you simply sleep cold: Therm-a-Rest NeoAir XTherm NXT, R-value 7.3, 440 g in Regular, with the tougher 70D underside.

If you are stopping at designated sites rather than carrying everything on your back, weight matters less and comfort matters more, so buy the thicker and warmer pad. Where those designated stopovers are and what they permit is in free camping in Europe, and the difference between a stopover and a wild pitch is in wild camping, free camping and aires.

More gear pages are in gear.

Sources

Where the original is not in English, the summary above is ours and the linked text is the authority.

Best sleeping pad for backpacking: R-value 3.2, 4.5 and 7.3 compared

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