Sleeping Pad R-Value: Why the Thickest Pad Is Not the Warmest
Two pads sit next to each other. One is four inches thick with a built-in foot pump. The other is two inches thick and rolls smaller. The thin one is nearly four times warmer. That is not a trick, it is what R-value measures, and it is the single most useful number on a camping pad.
What R-value actually is
R-value measures resistance to heat flowing through the pad into the ground. Higher is warmer. It says nothing about comfort, thickness or how nice the pad feels.
A thick air pad is mostly a bag of air, and air moves. Convection inside a big open chamber carries your body heat straight down to the cold ground. A self-inflating pad is foam that happens to hold air, and the foam traps the air in cells so it cannot circulate. That is why two inches of foam beats four inches of air.
The scale, in seasons
- Under R-2: summer only. You will feel the ground on a fall night.
- R-2 to R-3.5: three-season for warm sleepers, or summer with margin.
- R-4 to R-5: genuine shoulder season. Frost on the tent and you are still fine.
- R-5.5 and up: winter, frozen ground, snow.
Your sleeping bag rating assumes a pad is doing its half of the job. A 32F bag on an R-1 pad does not perform like a 32F bag, which is why people blame the bag for a cold night that the pad caused.
R-values stack
This is the cheapest trick in cold weather camping. Put a closed-cell foam mat under your inflatable pad and the two R-values add up, near enough. An R-3.8 pad on top of an R-2 foam mat gives you roughly R-5.8 for the price of a foam mat, and the foam doubles as a groundsheet and a seat.
The cot problem
Getting off the ground solves damp, bugs and lumps. It makes cold worse, because air circulates freely under a cot and takes your heat with it. A cot without a pad on top is a summer arrangement.
Our oversized cot runs 74.8 inches long and 26.3 inches wide on a steel tube frame rated to 330 lbs, which solves the tall-sleeper problem. Put a pad on it once the nights turn.
Our range, by the number
| Pad | R-value | Weight | Size |
|---|---|---|---|
| Double self-inflating, built-in pump | 7.5 | 9.7 lbs | 79 x 50.4 in, double |
| PARADOX 5 self-inflating | 4.2 | 3.3 lbs | 78 x 24.8 in, single |
| Self-inflating with built-in pillow | 3.8 | 2.6 lbs | 72 x 20 in, single |
| DELUXE 10.1 air pad, foot pump | 1.1 | 2.1 lbs | 74.8 x 27.6 in, single |
| 3.9 in insulated air pad | not published | 2 lbs | 74 x 24.8 in, single |
| GORGEOUS DOUBLE 17 air pad | not published | 9.1 lbs | 79 x 55.5 in, double |
Two of those do not have a manufacturer-published R-value. We are not going to estimate one for you. Both are insulated air constructions, so treat them as three-season until the figure is published.
Reading that table
The DELUXE 10.1 is the clearest example of the whole point of this article. Nearly four inches of loft, an integrated pillow, a foot pump so the bed builds itself after a driving day, and R-1.1. It is a genuinely comfortable summer and festival pad and a poor cold weather one.
The double self-inflating at R-7.5 is the opposite. Three inches of high-rebound foam, a 3D sidewall so the edges do not collapse, and enough insulation for frozen ground. It weighs 9.7 lbs, which is irrelevant in a truck.
For one person who wants a single sensible answer, the PARADOX 5 at R-4.2 and 3.3 lbs is it. Enough for shoulder-season cold, light enough not to think about.
Under all of it
A ground mat outside the tent is not insulation for sleeping, but it keeps sand and damp out of the living space and protects the tent floor from punctures. The ISIAY MAX is 9 by 9 feet with an aluminium film base, sized for awning and tailgate setups.
How to pick in one line
Decide the coldest night you actually camp in, pick R-4 or higher if that is below about 40F, and stack a foam mat under it if you go colder. Then choose thickness and width for comfort, not for warmth.
The rest of the range is in cots, pads and air mattresses. What goes on top of it is in sleeping bag temperature ratings, and if you are camping where the ground freezes, a canvas hot tent with a stove jack is the other half of the answer.