Sleeping mat R-value guide
The calculator needs JavaScript. The worked example, sum and figures below show exactly how it works, so you can do it yourself. A guide, not advice.
Short answer
Enter the R-value from one or two mat labels to compare them, and optionally add a figure you want to compare against. If you stack mats, the displayed sum is an estimate for comparison; check that the ratings are reported on a comparable basis. This tool does not turn R-value into a temperature or predict personal comfort.
Worked example
| You enter | Value |
|---|---|
| First mat's R-value from its label | 2 |
| Second mat's R-value | 1.5 |
| Comparison R-value from a maker or guide | 4 |
3.5 (entered mats: 2 + 1.5)
| Result | Value |
|---|---|
| Combined R-value estimate | 3.5 (entered mats: 2 + 1.5) |
| Comparison | Your entered value is 0.5 below the comparison figure. |
Show the working
- Combined comparison: 2 + 1.5 = 3.5
- Comparison figure: 4
How it works
- Single mat: use the R-value shown on its label
- Stacked mats: add their R-values as a comparison estimate when ratings use a comparable test basis
- R-value alone does not predict a personal comfort temperature
ASTM F3340 describes a test method for measuring camping mattress thermal resistance. Check how each maker reports its value before comparing.
Ground temperature and moisture, sleeping bag, body, tent, fit and personal comfort all matter. This guide does not convert an R-value to a safe or comfortable night-time temperature.
Our figures (adjustable)
These are our planning allowances and, once checked, typical figures with their sources. They aren't facts about your kit: change any of them in the calculator.
This calculator has no built-in defaults: every figure comes from you or your kit's own label.
What to buy
Shopping links will appear here once our retailer partners are confirmed. We don't rank kit by testing it: see our spec-based kit guides.
FAQs
What does a sleeping mat R-value mean?
It describes thermal resistance measured using a test method. ASTM F3340 is a standard method for measuring camping mattress thermal resistance. Check the mat maker's description and test basis.
Can I add two mat R-values?
The calculator adds the values you enter as a comparison estimate. Confirm that both ratings use a comparable test basis, and remember that real sleeping warmth depends on more than the mats.
Guides that use it
Camping in autumn
Camping in autumn: check overnight temperatures, bag ratings, mat insulation, wet kit and shorter daylight before you pitch.
How to stay warm camping
How to stay warm camping: match your sleeping bag and mat to the forecast, keep sleepwear dry, and never bring a flame heater into a tent.
Sleeping mat R-values explained
Sleeping mat R-values explained: what the figure measures, how mats are compared, and why the mat works alongside your sleeping bag.