Sleeping bag rating finder
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 overnight low from the forecast. Look for a bag whose comfort rating is at or below that figure, and a few degrees lower if you tend to feel the cold. Use the comfort rating, not the limit: the limit is a lower number and feels cold at that temperature for most people.
Worked example
| You enter | Value |
|---|---|
| Where the night-time low comes from | I have the forecast |
| Lowest temperature forecast overnight | 6 °C |
| I tend to feel the cold at night | Yes |
| How much warmer, if you feel the cold | 3 °C |
Look for a comfort rating of 3 °C or lower
| Result | Value |
|---|---|
| Comfort rating to look for (or lower) | 3 °C |
| Night-time low used | 6 °C |
The three ratings on the label
- Comfort: The lowest temperature at which a standard adult who sleeps cold (the standard uses a 'standard woman') is expected to sleep comfortably in a relaxed position. Use this figure when you choose a bag.
- Limit: The lowest temperature at which a standard adult who sleeps warm (a 'standard man') is expected to sleep curled up for eight hours. It's lower than comfort, so a bag sold on its limit figure will feel cold at that temperature for many people.
- Extreme: A survival-only figure: the lowest temperature at which a standard woman could stay for six hours without hypothermia. Never plan a trip around it.
Show the working
- Forecast low: 6 °C
- You feel the cold: 6 °C − 3 °C = 3 °C comfort rating or lower
How it works
- Night-time low = your forecast, or the typical low for the region and month (Met Office averages)
- Comfort rating to look for = the night-time low, or the low minus the margin if you feel the cold
- Your bag: its comfort rating against that figure (a lower number is a warmer bag)
Use the comfort rating, not the limit. The limit is lower, so a bag bought on its limit feels cold at that temperature for most people.
A bag only works as part of a system: what's under you matters as much. An airbed full of cold air can feel colder than the bag's rating suggests. Our guide to sleeping mats explains R-values.
Children's bags may be rated differently from adults' bags. Check with the maker how a child's bag was rated.
Comfort guidance only. Tents are colder than the forecast on a clear, still night in a dip, and warmer under trees.
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.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| How much warmer, if you feel the cold | 3 °C | Our assumption Not yet checked against the source | Our choice: change it to suit your trip How much warmer a bag to look for if you tend to sleep cold. Our assumption, not a standard figure. |
| Table | Clause | Nations | Status |
|---|---|---|---|
| Typical night-time lows by UK region and month | Met Office 1991–2020 climate averages, mean daily minimum temperature (Researcher to pick one representative station or regional series per row and cite it) | UK-wide | 0/84 values entered Not yet checked against the source |
| EN ISO 23537 sleeping-bag temperature ratings explained EN ISO 23537-1:2022 (Researcher to confirm the current edition and cite BSI or a maker's explainer) | The three temperatures on a rated bag's label, and what each means | UK-wide | 0/6 values entered Not yet checked against the source |
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's the difference between comfort and limit?
Both come from the EN ISO 23537 test. Comfort is for someone who feels the cold, sleeping relaxed; limit is for someone who sleeps warm, curled up. Shop by comfort.
Is a sleeping bag enough on its own?
No. What's underneath you matters as much. A thin mat or an airbed full of cold air can make a warm bag feel cold, so check your mat too.
Do children need a different rating?
Children feel the cold differently and their bags may be rated differently. Check with the maker how a child's bag was rated, and pack an extra layer for them.
Guides that use it
Camping in autumn
Camping in autumn: calm, practical help for UK families and first-timers, from the Canvasdale team.
How to stay warm camping
How to stay warm camping: calm, practical help for UK families and first-timers, from the Canvasdale team.
Sleeping bag temperature ratings explained
What the comfort, limit and extreme ratings on a sleeping bag label mean, which one to shop by, and how to match a bag to a British night.
Sleeping mat R-values explained
Sleeping mat R-values explained: calm, practical help for UK families and first-timers, from the Canvasdale team.
Best sleeping bags for camping (UK)
Best sleeping bags for camping (UK): calm, practical help for UK families and first-timers, from the Canvasdale team.
Camping in October half-term
Camping in October half-term: calm, practical help for UK families and first-timers, from the Canvasdale team.
Camping in spring
Camping in spring: calm, practical help for UK families and first-timers, from the Canvasdale team.