EN ISO 23537
EN ISO 23537 is the European standard method sleeping-bag makers use to state comfort, limit and extreme temperatures. When a maker follows it, the three figures come from the same method, which helps when you compare bags.
Where you'll see it
The standard may be named on a sleeping bag label, a product specification or the maker's website, beside the temperature figures. If a bag lists temperatures but never names a standard, ask the maker how its figures were worked out before you rely on them.
What to check
- Whether the label or product page names EN ISO 23537 next to the temperature figures.
- Which figure is labelled comfort, since that is the one to compare.
- Whether the maker has published an explainer or a note on how the figures apply.
- Whether the rating assumes a particular mat, liner or set of clothing.
Related terms
- Comfort rating: the figure to compare when bags name the standard.
- Limit rating: one of the three figures the standard is used to state.
- Season rating: a label that may not say how it was measured.
Read more: sleeping bag temperature ratings explained and, if one fits, the sleeping bag rating calculator.