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⚡ Quick Answer: R-value measures resistance to heat loss through the pad. Roughly: under 2 is summer only, 2 to 4 covers three-season use, 4 to 5.5 handles freezing nights, and above 5.5 is for winter and snow. If you sleep cold or are a side sleeper who compresses the pad, go one step higher than the chart suggests.
If you have ever gone to bed in a warm sleeping bag and woken up cold on one side, you have met the problem R-value describes. The ground is an enormous heat sink, and it does not care what your bag is rated for. R-value is the single number that tells you how well a pad stands between you and it.
What the number means
R-value is resistance to heat flow, and it is linear and additive. A pad with an R-value of 4 resists roughly twice as much heat loss as one rated 2, and stacking a 2 under a 3 gives you about 5. Since 2020 there is a shared industry test, so numbers from major brands can be compared directly, which was not true before.
What each range is actually for
- Under 2: warm summer nights, above about 15 degrees Celsius. Fine for a July trip at low elevation, cold in the mountains even in August.
- 2 to 4: three-season use, comfortable down to around freezing for most people. This is where the majority of backpacking pads sit and where most beginners should start.
- 4 to 5.5: reliably below freezing, late autumn and early spring, frozen ground. A good choice if you already know you sleep cold.
- Above 5.5: winter camping, snow, sustained deep cold. Usually achieved with a thick inflatable, or an inflatable plus a closed-cell foam pad underneath.
One honest caveat: these ranges assume an average sleeper on a properly inflated pad. Side sleepers compress a pad much harder at the hip and shoulder, and people who run cold notice a difference of a full point. If either describes you, take one step up.
Why the pad matters more than the bag
Insulation works by trapping air. Above you, your sleeping bag lofts freely and does its job. Below you, your body weight crushes that same insulation flat, and flat insulation insulates very little. This is why a 20 degree bag on a summer pad is cold, and a 30 degree bag on a good winter pad is often fine.
So if you are cold at night and about to buy a warmer bag, check your pad first. It is usually the cheaper fix and almost always the more effective one. Bag ratings themselves are their own minefield, unpacked in sleeping bag temperature ratings explained and how to choose a sleeping bag.
The stacking trick
The most cost-effective way to handle a wide temperature range is to own a three-season inflatable pad plus a cheap closed-cell foam pad. In summer, take the inflatable. In deep cold, take both. R-values add, so you get winter performance without buying a second expensive pad, and the foam layer protects the inflatable from sharp ground.
Foam also fails gracefully. An inflatable that punctures at 2am in February is a serious problem; foam cannot deflate.
Things that quietly cost you warmth
- Underinflation. A soft pad lets your hip touch through to the ground. Firm enough that you do not bottom out when you press down hard with a fist.
- Going to bed cold. A pad and bag conserve heat; they do not create it. Do some light movement and eat something before you get in.
- Damp insulation. Condensation inside a bag or a wet pad surface both move heat away faster.
- Sleeping directly on snow without clearing and compacting it. Uneven snow melts under warm spots and refreezes into cold conducting bridges.
- A thin cotton base layer. What you wear to bed matters, and cotton is the wrong choice; see our base layer guide.
Choosing in practice
For a first pad, buy something in the 3 to 4.5 range. It covers spring through autumn in most places, it is not absurdly heavy, and you will not immediately need to replace it when the nights turn. Then add a foam pad later if winter becomes interesting. Our sleeping pad roundup covers current options, and if you are deciding between a backpacking pad and something plusher for car camping, see sleeping pad vs air mattress.
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Frequently Asked Questions
Is R-value standardised between brands?
Since 2020 there is an industry test standard, ASTM F3340, and most major brands now publish numbers measured that way, which makes them genuinely comparable. Older pads and some budget brands use in-house figures that tend to be optimistic.
Can I stack two pads?
Yes, and R-values add together, near enough. A 2.0 foam pad under a 3.0 inflatable gives you about 5.0. This is the cheapest way to extend a three-season pad into winter, and the foam pad also protects the inflatable from punctures.
Does a warmer bag fix a cold pad?
No, and this is the most common beginner mistake. Insulation under you gets compressed by your body weight, so it loses most of its loft and most of its insulating value. The ground will pull heat out from underneath no matter how good the bag is above you.
Why am I cold on a pad rated for the temperature?
Usually one of four reasons: you are a side sleeper compressing the pad at hip and shoulder, you sleep cold generally, the pad is underinflated, or you went to bed already chilled and without enough calories to generate heat.
Do I need a higher R-value on a cot or in a hammock?
On a cot you have air moving under you, which needs a pad too, though a modest one. In a hammock, the compression underneath is severe and a pad often shifts; most hammock campers use an underquilt instead, which hangs below and does not compress.
Does R-value affect comfort?
Not directly. Comfort comes from thickness and internal structure. A thick pad often has a higher R-value as a side effect, but the two are separate specs and you should check both.
Written by Jake Miller · Camping & Gear
Jake grew up pitching tents before he could drive and has spent 15+ years camping, car-camping, and gear-testing his way across the country. If it can be cooked over a fire or packed into a trunk, he has an opinion on it.
