🛏️ Sleeping Pad R-Value Guide
The pad, not the bag, is what stops the cold ground stealing your warmth. Enter the overnight low to see the minimum R-value you need, look up what any R-value handles, and stack two pads to reach winter warmth — all from the standardised ASTM F3340 test.
🛏️ Recommended pad
An R3 pad is comfortable to roughly 0 °C. Sizing up an R-value adds a useful margin on a cold night.
Stack two pads (R-values add)
Because R-values add, a closed-cell foam pad under an inflatable is a cheap, reliable way to reach winter warmth — and the foam layer is a backup if the inflatable punctures.
R-value reference (ASTM F3340)
| R-value | Comfortable to | Season |
|---|---|---|
| R1 | +7 °C | Summer |
| R2 | +2 °C | Warm 3-season |
| R3 | 0 °C | 3-season |
| R4 | -5 °C | Cold 3-season |
| R5 | -11 °C | Winter |
| R6 | -17 °C | Cold winter |
| R7 | -24 °C | Deep winter / snow |
Cold ground pulls heat from your body far faster than cold air, so on a chilly night the pad matters as much as the sleeping bag. Treat these as planning figures — your bag, sleep style, and the ground all shift the real comfort point.
One standard, comparable numbers
Before ASTM F3340, every brand tested pads its own way and R-values couldn't be trusted across companies. The standard fixed that: an R-value is now a like-for-like measure of warmth, so you can shop on the number with confidence.
The other rule to remember is that pads stack — their R-values add. That turns a modest three-season pad into a winter setup with a cheap foam pad underneath, and gives you a fail-safe if an inflatable springs a leak far from anywhere.
❓ Frequently Asked Questions
What is a sleeping pad R-value?
R-value measures how well a sleeping pad resists heat flowing from your body into the cold ground — the higher the number, the better the insulation. Since 2018 the ASTM F3340 standard has given every brand one common test method, so an R4 from one company now means the same warmth as an R4 from another. Values run from about 1 for bare-summer pads to 7 or more for deep-winter mountaineering pads.
What R-value do I need for the temperature?
As a rough guide, R1 is comfortable to around +7 °C for summer, R3 to about 0 °C for three-season use, R5 to roughly −11 °C for winter, and R7 and up for deep winter and snow. These are planning figures: your sleeping bag, how warm you sleep, and how cold and damp the ground is all shift the real comfort point, so size up if in doubt.
Do R-values really add when you stack pads?
Yes — that's one of the most useful facts in cold-weather camping. Layered pads insulate additively, so an R2 foam pad under an R3 inflatable gives you R5, enough for winter. Stacking is a cheap, reliable way to extend a three-season pad into winter, and the closed-cell foam layer doubles as a puncture-proof backup if the inflatable fails overnight.
Why does the ground matter more than the air?
When you lie down, your body weight crushes the insulation of your sleeping bag underneath you, and the ground conducts heat away far faster than still air ever could. That's why a warm bag on a thin pad still leaves you cold from below. The pad's R-value, not the bag, is what stops that heat loss, so in cold conditions the pad is at least as important as the bag.
Does a higher R-value make a pad heavier or less comfortable?
Not necessarily. Modern pads use reflective films and baffled construction to hit high R-values without much weight penalty, so a warm winter pad need not be a heavy one. Comfort comes mostly from thickness and shape rather than R-value, so choose the R-value for the season and the thickness for a good night's sleep — they're largely independent.